Serum thyroid hormones and thyroid hormone binding were sequentially measured in 20 patients with acute hepatitis B infection. Criteria to select patients consisted of a positive test for hepatitis B surface antigen, aspartate aminotransferase (AsAT) concentration greater than 400 U/L during the acute illness, and available serum specimens after recovery. The mean serum thyroxine (T4) concentration (+/- SE) was 12.5 +/- 0.6 microgram/dL during acute infection and 7.4 +/- 0.3 microgram/dL after recovery (p less than 0.001), whereas mean free T4 index values did not significantly differ. The mean serum thyroxine-binding globulin (TBG) concentration was significantly increased (p less than 0.001) during acute illness and accounted for the reversible of serum and the increased serum T4 concentrations. The rise in serum TBG correlated with the rise in AsAT during the acute illness (p less than 0.04) suggesting nonspecific release of these proteins from injured hepatocytes. The mean free triiodothyronine (T3) index was decreased during acute hepatitis (p less than 0.001) and returned to normal after recovery, indicating that acute hepatitis B infection, like other nonthyroidal illnesses, is associated with decreased T4 to T3 conversion in peripheral tissues.

BACKGROUND

We studied serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), triiodothyronine (T3), free T3 (FT3), cortisol and growth hormone (GH) concentrations in a population of pediatric patients. The reference intervals were determined separately for females and males stratified by age groups to assess age- and sex-related differences. Our objective was to obtain reference intervals for the 7 serum analytes for our pediatric population using the IMMULITE 1000 system.

METHODS

Serum samples of 800 in- and out-patients, newborn to 19 years old were analyzed using the DPC IMMULITE 1000 chemiluminescent immunoassay system.

CONCLUSIONS

We report pediatric reference intervals for FSH, LH, E2, T3, FT3, cortisol, and GH. These reference intervals provide the basis for clinical interpretation of laboratory results using the IMMULITE 1000 system and the assessment of child development.

OBJECTIVE

Exposure of the thyroid to therapeutic doses of external irradiation has been demonstrated to induce thyroid dysfunction. This study was designed to assess the relationship between irradiation and early thyroid dysfunction, prospectively.

METHODS

Twenty patients in whom the thyroid was incidentally exposed to therapeutic doses of irradiation were studied. The dose given to the thyroid was 40-54 Gy over 4-7 weeks. Thyroid function tests, including serum thyroid stimulating hormone (TSH), free thyroxine (free T4), free triiodothyronine (free T3), antithyroglobulin antibody, and antimicrosomal antibody, were performed prior to irradiation and at 3, 6, and 12 months after radiotherapy.

RESULTS

Serum TSH levels did not change significantly at 3 months after irradiation (mean TSH level: 1.33 microU/ml before irradiation, 1.74 microU/ml at 3 months, p = 0.11). However, a significant elevation was noted at 6 months (mean TSH: 3.50 microU/ml at 6 months, p = 0.0001, vs. preirradiation), when TSH levels were higher than preirradiation levels in 19 of 20 patients. After irradiation, 13 patients remained in a euthyroid state (euthyroid group), while in the other 7 patients hypothyroidism occurred (hypothyroid group) and thyroid hormone-replacement therapy was performed. After 6 months, elevation of TSH was less significant in the euthyroid group, whereas elevation of TSH persisted continuously and exponentially in the hypothyroid group. Thyroid autoantibodies did not turn positive in any patient during follow-up.

CONCLUSIONS

Damage of the thyroid develops in most patients when the organ is exposed to radiation. This radiation-induced damage is initially manifested within 6 months after irradiation.

Polychlorinated biphenyls (PCBs), persistent chemicals widely used for industrial purposes, have been banned in most parts of the world for decades. Owing to their bioaccumulative nature, PCBs are still found in high concentrations in marine mammals, particularly those that occupy upper trophic positions. While PCB-related health effects have been well-documented in some mammals, studies among dolphins and whales are limited. We conducted health evaluations of bottlenose dolphins (Tursiops truncatus) near a site on the Georgia, United States coast heavily contaminated by Aroclor 1268, an uncommon PCB mixture primarily comprised of octa- through deca-chlorobiphenyl congeners. A high proportion (26%) of sampled dolphins suffered anaemia, a finding previously reported from primate laboratory studies using high doses of a more common PCB mixture, Aroclor 1254. In addition, the dolphins showed reduced thyroid hormone levels and total thyroxine, free thyroxine and triiodothyronine negatively correlated with PCB concentration measured in blubber (p = 0.039, < 0.001, 0.009, respectively). Similarly, T-lymphocyte proliferation and indices of innate immunity decreased with blubber PCB concentration, suggesting an increased susceptibility to infectious disease. Other persistent contaminants such as DDT which could potentially confound results were similar in the Georgia dolphins when compared with previously sampled reference sites, and therefore probably did not contribute to the observed correlations. Our results clearly demonstrate that dolphins are vulnerable to PCB-related toxic effects, at least partially mediated through the endocrine system. The severity of the effects suggests that the PCB mixture to which the Georgia dolphins were exposed has substantial toxic potential and further studies are warranted to elucidate mechanisms and potential impacts on other top-level predators, including humans, who regularly consume fish from the same marine waters.

A prospective study was undertaken to evaluate urinary iodine excretion and changes of maternal thyroid function during pregnancy in healthy women living in the southwest of France. The cohort included a total of 347 pregnant women (mean age 28.0+/-0.5 years). Iodine concentration in a random urine sample and thyroid tests (free thyroxine [FT4], free triiodothyronine [FT3], thyrotropin (TSH), thyroxine-binding globulin [TBG], and thyroglobulin [Tg]) were measured at initial presentation (before 12 weeks of gestation), and during the ninth month of pregnancy. A thyroid ultrasound was performed 1 to 5 days after delivery in 246 mothers. Mean urinary iodine levels were low during the first trimester (6.9+/-0.4 microg/dL), as well as during the ninth month of pregnancy (8.6+/-0.6 microg/dL). During pregnancy, FT4 and T3 concentrations decreased (p < .001), and TSH and Tg concentrations increased (p < .001). Thyroid hypertrophy (thyroid volume greater than 18 mL) was present in 15.4% of women whose first trimester urinary iodine concentration was less than 5 microg/dL, but was present in only 3.5% of women whose urinary iodine concentration was greater than 10 microg/dL. A goiter (thyroid volume greater than 22 mL) was present in 11% of the mothers. In conclusion, this prospective study shows that urinary iodine excretion is low in pregnant women living in the southwest of France. This low iodine intake is associated with reduced circulating thyroid hormone levels and growth of the thyroid gland. These data point to the need of an increased iodine supply in these pregnant women to reduce the potential consequences of low iodine intake on maternal thyroid economy.

In a randomized, double-blind, placebo-controlled, cross-over study, we examined the effects of 14 days of growth hormone (GH) administration (12 IU/d subcutaneously) on energy expenditure (EE), respiratory exchange ratio (RER), and thyroid function in 14 normal adults of normal weight (eight men and six women). EE (kcal/24 h) was significantly elevated after GH administration (2,073 +/- 392, [GH], 1,900 +/- 310, [placebo], P = .01). RER was significantly lowered during GH administration (0.73 +/- 0.04 v 0.78 +/- 0.06, P = .02), reflecting increased oxidation of lipids. Total triiodothyronine (TT3) (nmol/L) and free T3 (FT3) (pmol/L) increased significantly during GH (TT3: 1.73 +/- 0.06 [GH], 1.48 +/- 0.08 [placebo], P = .01; FT3: 6.19 +/- 0.56 [GH], 5.49 +/- 0.56 [placebo], P = .01). Concomitantly, an insignificant decrease in reverse T3 (rT3) (nmol/L) was observed (0.07 +/- 0.01 [GH], 0.15 +/- 0.01 [placebo], P = .08). GH caused a highly significant increase in T3/thyroxine (T4) (x 100) ratio (1.84 +/- 0.12 [GH], 1.37 +/- 0.06 [placebo]). Serum thyrotropin (TSH) was not significantly changed by GH. No changes in total thyroxine (TT4) (nmol/L) (98 +/- 6 [GH], 111 +/- 8 [placebo], P = .40) and free thyroxine (FT4) (pmol/L) (17.4 +/- 1.3 [GH], 18.6 +/- 1.1 [placebo], P = .37) after 14 days of GH administration were observed. In conclusion, 2 weeks of GH administration increases EE and lipidoxidation. This finding may partly be mediated by an increase in peripheral T4 to T3 conversion.

A group of 80 menstruating rhesus (Macaca mulatta) monkeys, with an average estimated age of 11.1 +/- 4.1 yr SD were first randomly allocated to four similar test rooms (20 monkeys/room), and then randomly allocated to one of five dose groups (four females/dose group/room). Each day, the monkeys self-ingested capsules containing doses of 0, 5, 20, 40 or 80 micrograms Aroclor 1254/kg body weight. After 25 months of daily dosing, approximately 90% of the treated females attained a qualitative pharmacokinetic steady state with respect to the concentration of polychlorinated biphenyl (PCB) in their adipose tissue. Subsequently, oestrogen and progesterone concentrations in serum were determined for one complete oestrous cycle and various immunological tests were conducted, while the monkeys continued to receive their daily dose of PCB. During the prebreeding phase of the study, blood for clinical and analytical monitoring including haematology, serum biochemistry, serum hydrocortisone, serum proteins (alpha 1, alpha 2, beta and gamma-globulins), serum immunoglobulins (A, G and M) and thyroid variables (thyroxine/triiodothyronine (T3) uptake ratio, percentage T3 uptake and free thyroxine index), were obtained monthly, as were specimens to ascertain the concentration of PCB in the blood, adipose tissue and faeces. Major findings among treated monkeys included the following: changes in haematology (decreased erythrocyte count, haematocrit, reticulocyte count, and mean platelet volume), serum biochemistry (decreased cholesterol and total bilirubin), immunotoxicity (decreased antibody production to sheep red blood cells and alterations in the percentage of T helper and T suppressor cells) and pathology (the number of regions of sebaceous gland lobules per unit of histological length was significantly reduced). These effects were observed at PCB doses lower than those previously reported for non-human primates.

Hypothalamic amenorrhea in anorexia nervosa often precedes weight loss and may persist after re-feeding and restoration of a stable normal weight.

OBJECTIVE

To assess the rate of persistent amenorrhea in anorexia nervosa (AN) after re-feeding and the relations of this condition with body composition changes and other endocrine parameters.

METHODS

A cohort of 250 female outpatients was studied to assess persistent amenorrhea prevalence after stable weight recovery. Among these, we selected 20 AN female patients (age 16.5-35), 10 with amenorrhea (group 1) and 10 with normal menses (group 2). We collected data such as age, age at menarche, age at onset of AN, actual body mass index (BMI) and at onset of AN, duration of disease. Physical activity has been evaluated as minute per day. The following data were obtained: prolactin, growth hormone, estradiol, luteinizing hormone, follicle stimulating hormone, thyroid stimulating hormone, free triiodothyronine, free thyroxine, free urinary cortisol, serum calcium and phosphates, urinary calcium, phosphaturia and alkaline phosphatase. Body composition was assessed with a dual energy x-ray absorptiometry (DEXA).

RESULTS

Thirty-five patients (14%) over a cohort of 250 where still amenorrhoic after stable weight recovery. No significance was found in the evaluation of blood biochemical tests of the 2 groups. Free urinary cortisol was significantly higher in amenorrhoic patients (58.14+/-0.4 vs 15.91+/-9.5), p=0.02. The analysis of body composition has shown a percentage of fat of 22.23+/-5.32% in group 1 and of 26.03%+/-9.1% in group 2, respectively, showing no significant differences. Amenorrhoic patients carried on doing a significantly heavier physical activity than eumenorrhoic patients.

CONCLUSIONS

An adequate body composition and a well represented fat mass are certainly a necessary but not sufficient condition for the return of the menstrual cycle. Such menstrual cycle recovery would probably need other conditions at present being studied and evaluated to occur, such as secretory patterns of leptin and its correlations with adrenal function.

OBJECTIVE

To test the hypothesis that triiodothyronine (T(3)) administration improves hemodynamic variables and decreases inotropic drug requirements in cardiac surgery patients.

METHODS

Prospective, randomized, double-blind, placebo-controlled trial.

METHODS

Tertiary care medical center.

METHODS

A total of 211 patients undergoing coronary artery surgery at high risk for requiring inotropic drug support.

METHODS

At release of aortic cross-clamp, patients were randomized to an intravenous infusion of T(3) (0.8 microg/kg followed by 0.12 microg.kg(-1).h(-1) for 6 hours), dopamine (positive control, 5 microg.kg(-1).min(-1) for 6 hours) or placebo.

METHODS

Perioperative hemodynamic variables, inotropic support requirements, and serum T(3) concentrations.

RESULTS

Mean+/-SEM free T(3) serum concentrations decreased significantly during cardiopulmonary bypass in all groups (from 0.0035+/-0.0001 nmol/L [0.23+/-0.01 ng/dL] to 0.001+/-0.0001 nmol/L [0.7+/- 0.00 ng/dL]; P=.001) and increased to 0.0133+/-0.0004 nmol/L [0.87+/-0.03 ng/dL] (twice normal range; P<.001) following initiation of intravenous T(3). Intravenous T(3) did not change hemodynamic variables or inotropic drug requirements; however, heart rate increased (P<.001), and a trend toward decreased use of inotropic agents was demonstrated in the dopamine group.

CONCLUSIONS

Triiodothyronine administration prevents decreases in serum thyroid hormone concentrations associated with cardiopulmonary bypass. Intravenous T(3) does not have dramatic effects on hemodynamic variables in this setting as has been previously suggested. Although mild effects on myocardial performance may exist, we cannot recommend at this time the routine use of intravenous T(3) as an inotropic agent in patients undergoing coronary artery bypass graft surgery.

BACKGROUND

The relationship between subclinical hypothyroidism (SCH) and cardiovascular disease is not fully understood. We investigated risk factors for cardiovascular disease (lipid profile, lipoproteins, insulin resistance, C-reactive protein [CRP] homocysteine [Hcy] and fibrinogen levels) and their relationships with thyroid hormones in SCH patients and controls.

METHODS

Thirty-eight SCH patients and 44 controls were enrolled in this study. No patients had any substantial confounding medical conditions (including diabetes mellitus or coronary heart disease) or were taking thyroid-related medication.

RESULTS

Serum total cholesterol (P<0.05), low-density lipoprotein cholesterol (P<0.05) and triglycerides (P<0.001) were higher in patients with SCH than in controls. Serum lipoprotein(a) (Lp[a]) levels were higher in SCH subjects but this difference did not reach statistical significance (P=0.07). No significant differences were noted in CRP, Hcy, fibrinogen, high-density lipoprotein cholesterol, apolipoprotein A-1, apolipoprotein B (Apo B) or insulin resistance between patients with SCH and controls (in all cases, P>0.05). Free triiodothyronine (FT3) negatively correlated with Apo B (r=.0.46, P=0.005) and Lp(a) (r=.0.31, P=0.03) in patients with SCH and negatively correlated with Lp(a) (r=.0.30, P=0.04) in controls. All of these parameters were comparable between patients with thyroid-stimulating hormone (TSH) >10 microIU/ml and TSH <10 microIU/ml (in SCH patients, P>0.05).

CONCLUSIONS

Our results suggest that SCH is associated with some lipid and lipoprotein abnormalities. Our results also suggest that this association does not depend on the subject's TSH level.

Populations of scavenging seabird species in the North Sea may fluctuate with an artificial food source: the availability of fishery waste. To document this impact, it is necessary to assess the birds' nutritional status during periods with decreased fishing activity. Reference data for this purpose was collected from 22 herring gulls investigated during laboratory fasting. After 6 d of food deprivation and body mass losses exceeding 15%, the first birds entered starvation phase 3. Comparatively, this is a rather weak fasting capacity. Plasma levels of total protein and thyroid hormones decreased and beta-hydroxybutyrate increased with fasting duration. The leucocyte proportions were shifted from lymphocytes to heterophils. After 3 d of refeeding, most of the fasting changes were reversed. Plasma enzyme activities increased and hematocrit, hemoglobin, and erythrocyte numbers decreased in both fasting and control birds, most likely as a result of experimental stress and repeated blood sampling. Glucose, cholesterol, monocytes, basophils, and glycosylated hemoglobin remained fairly constant. Triglycerides, free fatty acids, uric acid, and urea varied significantly, but changes were not as clearly a result of fasting. Therefore, total protein, beta-hydroxybutyrate, triiodothyronine, thyroxine, and lymphocyte and heterophil percentages may be the most reliable indicators of the nutritional status and the condition of free-living herring gulls.

OBJECTIVE

To determine whether cytokine release or activation of the hypothalamo-pituitary-adrenal (HPA) axis is predominantly involved in the development of the euthyroid sick syndrome (ESS).

METHODS

Prospective observational study.

METHODS

Intensive care unit at a tertiary care medical center in Germany.

METHODS

Nine patients with sepsis of different causes and eight patients with acute myocardial infarction.

METHODS

None.

RESULTS

Immediately on admission and on day 7 the following parameters were determined: total thyroxine (T4), free thyroxine (FT4), total triiodothyronine (T3), thyrotropin (TSH), interleukin-1 beta (IL-1 beta), interleukin-2 (IL-2), soluble interleukin-2 receptor (sIL-2R), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), serum cortisol and plasma adrenocorticotropin (ACTH). On admission, concentrations of all thyroid hormones and TSH were significantly lower in septic patients compared to non-septic patients, whereas all cytokines except IL-2 were significantly elevated in the sepsis group. By contrast, there was no difference in serum cortisol and plasma ACTH levels between the two groups. On day 7, T4 and T3 were still lower in the septic group, whereas IL-1 beta, sIL-2R and IL-6 were still elevated. Again, no differences were found with regard to cortisol and ACTH levels.

CONCLUSIONS

Euthyroid sick syndrome occurs very early during the course of septic diseases. Significantly decreased levels of total T4, FT4, T3 and TSH in septic patients suggest central suppression of TSH as well as inhibition of thyroid hormone release in ESS. The HPA axis is activated in septic patients and in non-septic patients and does not contribute to the development of ESS.

An 8-year old boy with a small goiter, normal basal metabolic rate (BMR), and elevated serum thyroid hormone levels (thyroxine [T(4)] 19.5 mug per 100 ml, free T(4) 4 ng per 100 ml, triiodothyronine [T(3)] 505 ng per 100 ml) was studied. He had measurable serum thyroid-stimulating hormone (TSH) levels (average 5.5 muU per ml), and the thyroxine-binding proteins, hearing, and epiphyseal structures were normal. There was no parental consanguinity nor were there thyroid abnormalities either in the parents or six siblings.Methimazole, 50 mg daily, depressed thyroxine synthesis (T(4) 10.5, free T(4) 2.5) and caused a rise in TSH to 11 muU per ml. After discontinuation of treatment, TSH declined to 4.2 muU per ml and chemical hyperthyroidism returned (T(4) 21.0 mug per 100 ml, free T(4) 4.2, and total T(3) 475 ng per 100 ml, radioactive iodine [RAI] uptake 68%), but studies of BMR and insensible water loss showed the patient to be clinically euthyroid. Thyrotropin-releasing hormone (TRH), 200 mug i.v., caused a brisk rise in TSH to 28 muU per ml, with T(4) rising to 28 mug per 100 ml, free T(4) to 5.6, and T(3) to 730 ng per 100 ml, thus indicating that the pituitary-thyroid system was intact and that the patient's TSH was biologically active. The unusual sensitivity of the pituitary cells to TRH in spite of the markedly elevated serum thyroid hormone levels also suggested that the pituitary was insensitive to suppression by T(3) or T(4). Serum dilution studies gave immunochemical evidence that this patient's TSH was normal. Neither propranolol, 60 mg, chlorpromazine, 30 mg, nor prednisone, 15 mg daily, influenced thyroid indices. Steroid treatment, however, suppressed the pituitary response to TRH, T(3) in doses increased over a period of 12 days to as much as 150 mug daily caused a rise in serum T(3) to above 800 ng per 100 ml, a decline of T(4) to euthyroid levels (T(4) 9.5 mug per 100 ml, free T(4) 1.6 ng per 100 ml), suppression of the RAI uptake from 68% to 35%, and marked blunting of the responses to TRH, but the BMR and insensible water loss remained normal. The data suggest that the patient's disorder is due to partial resistance to thyroid hormone.

OBJECTIVE

To determine whether subclinical hypothyroidism (SCH) alters the phenotype, insulin resistance, or lipid parameters in young women with polycystic ovary syndrome (PCOS).

METHODS

Prospective case-control study.

METHODS

Tertiary care setting.

METHODS

Sixty-two young women with PCOS and SCH (group I) and 291 euthyroid women with PCOS (group II).

METHODS

Recording of clinical, biochemical, hormonal profile, and parameters of insulin resistance.

METHODS

Whether SCH has any association with clinical parameters like hirsutism, menstrual disturbances, lipid profile, and parameters of insulin sensitivity.

RESULTS

Mean (±SD) TSH was 7.13±1.28 IU/L in group I and 2.51±1.21 IU/L in group II, with comparable free triiodothyronine and free thyroxine. The two groups were comparable in age, weight, and body mass index. Parameters like blood pressure, menstrual pattern, and degree and duration of hirsutism did not differ between the two groups. Serum concentrations of triglycerides were significantly higher in the SCH group compared with controls. Plasma glucose concentrations both in fasting and after oral glucose tolerance test were similar between the two groups. Fasting insulin and other parameters of insulin resistance were not altered by SCH.

CONCLUSIONS

Mild TSH elevation in the face of normal serum free triiodothyronine and free thyroxine results in a mild increase in serum lipids. Subclinical hypothyroidism is not associated with alteration in phenotypic expression and insulin resistance in young women with PCOS.

Measurements of serum levels of thyroxine (T4), free T4, 3,5,3'-triiodothyronine (T3), free T3, 3,3',5'-triiodothyronine (reverse T3, rT3), thyroxine-binding globulin capacity (TBGcap), chorionic gonadotrophin (hCG) and thyrotrophin (TSH) were carried out prospectively in eight women with uncomplicated pregnancies, in order to examine interrelationships between the thyroid gland and thyroid stimulating hormones during pregnancy. During pregnancy the levels of T4, free T4, T3, rT3 and TBGcap were significantly elevated, and TSH was decreased. It was noted that the elevation of T4 was maintained from the 8th to the 27th week of gestation while the level of TBGcap progressively increased. The levels of free T4 and rT3 in the first and third trimesters were significantly higher than those of age-matched, non-pregnant women. The levels of hCG showed a biphasic variation, with a peak in the 8th to 15th weeks, followed by a decline in the second trimester and a small, secondary elevation in the 32nd to 39th weeks. This later elevation was positively correlated with changes in free T4 and free T3 levels. The increase of serum T4 accompanied by an increase of free T4 in the first trimester appeared due to augmented secretion of T4, rather than being secondary to the elevated levels of TBGcap.

OBJECTIVE

To determine whether environmental perchlorate exposure adversely affects thyroid function in women in the first trimester of pregnancy.

METHODS

First-trimester pregnant women were recruited from prenatal clinics in the Los Angeles County Hospital, Los Angeles, California, and in the Hospital Universitario de Maternidad dependent Universidad Nacional de Córdoba, Córdoba, Argentina, between 2004 and 2007. Spot urine and blood specimens were obtained during the clinic visit. Urinary perchlorate, iodine, and creatinine were measured, and thyroid function tests were performed.

RESULTS

The study included 134 pregnant women from Los Angeles, California (mean gestational age ± SD = 9.1 ± 2.2 weeks), and 107 pregnant women from Córdoba, Argentina (mean gestational age = 10.0 ± 2.0 weeks). Median urinary iodine values were 144 μg/L in California and 130 μg/L in Argentina. Urinary perchlorate levels were detectable in all women (California: median, 7.8 μg/L [range, 0.4-284 μg/L] and Argentina: median, 13.5 μg/L [range, 1.1-676 μg/L]). Serum thyroperoxidase antibodies were detectable in 21 women from California (16%) and in 17 women from Argentina (16%). Using Spearman rank correlation analyses, there was no association between urinary perchlorate concentrations and serum thyrotropin, free thyroxine index, or total triiodothyronine values, including within the subset of women with urinary iodine values less than 100 μg/L. In multivariate analyses using the combined Argentina and California data sets and adjusting for urinary iodine concentrations, urinary creatinine, gestational age, and thyroperoxidase antibody status, urinary perchlorate was not a significant predictor of thyroid function.

CONCLUSIONS

Low-level perchlorate exposure is ubiquitous, but is not associated with altered thyroid function among women in the first trimester of pregnancy.

OBJECTIVE

Low triiodothyronine levels, as part of the nonthyroidal illness syndrome, are common in dialysis patients and have repeatedly been shown to be associated with increased (cardiovascular) mortality rates. We hypothesized that increased vascular calcification may mediate this relationship.

METHODS

A total of 84 patients from the Stockholm region receiving maintenance peritoneal dialysis were included in the study. Serum concentrations of free triiodothyronine (fT3), thyroxine and thyroid-stimulating hormone were measured. Coronary artery calcium (CAC) scores were assessed by cardiac computed tomography scans. Surrogates of arterial stiffness included aortic diastolic and systolic blood pressures, pulse pressure, augmentation pressure and Buckberg's subendocardial viability ratio measured by pulse waveform analyses. Patients were subsequently followed, and events of death and censoring were recorded. Thyroid hormone concentrations were associated with CAC scores, measures of arterial stiffness and all-cause mortality. The associations between CAC scores and arterial stiffness surrogates and mortality were also determined to evaluate a possible causal pathway.

RESULTS

Both CAC scores and arterial stiffness surrogates were substantially higher in individuals with low fT3 levels. These associations persisted in multivariate logistic and linear regression analyses. During a median (interquartile range) follow-up of 32 (22-42) months, 24 patients died. Both fT3 levels below the median value [HR crude 4.1, 95% confidence interval (CI) 1.4-12.6] and CAC scores above the median value (HR crude 5.8, 95% CI 1.7-20.1) were strongly associated with mortality.

CONCLUSIONS

In patients undergoing peritoneal dialysis, fT3 levels were strongly associated with arterial stiffness, coronary artery calcification and mortality. We speculate that the association between nonthyroidal illness and mortality may be partly mediated by acceleration of vascular calcification.

Thyroid function was studied in 54 patients undergoing chronic hemodialysis. Serum thyroxine, triiodothyronine and free thyroxine and the free thyroxine index were significantly lower than normal. The levels of both serum thyroxine and the free thyroxine index tended to fall progressively the longer the patients were on hemodialysis. These findings, in association with low serum TSH levels and normal increase in radioactive iodine uptake by the thyroid after TSH injection, suggest that a defect in pituitary secretion of TSH may be responsible. Although some patients experienced symptomatic improvement after treatment with L-thyroxine the efficacy of this form of treatment in patients on chronic hemodialysis has not yet been established.

BACKGROUND

Factors that influence energy metabolism and substrate oxidation, such as thyroid hormones (THs), may be important regulators of body weight.

OBJECTIVE

We investigated associations of THs cross-sectionally with obesity, energy expenditure, and substrate oxidation and prospectively with weight change.

METHODS

Euthyroid, nondiabetic, healthy, adult Pima Indians (n = 89; 47 M, 42 F) were studied. Percentage body fat (%BF) was measured by using dual-energy X-ray absorptiometry; sleeping metabolic rate (SMR), respiratory quotient, and substrate oxidation rates were measured in a respiratory chamber. Thyroid-stimulating hormone (TSH), free thyroxine (T(4)), free triiodothyronine (T(3)), and leptin concentrations were measured in fasting plasma samples.

RESULTS

TSH, but neither <em>free</em> T(3) nor <em>free</em> T(4), was associated with %BF and leptin concentrations (r = 0.27 and 0.29, respectively; both: P <or= 0.01). In multiple regression analyses adjusted for age, sex, fat mass, and fat-<em>free</em> mass, <em>free</em> T(3) was a positive predictor of SMR (P = 0.02). After adjustment for age, sex, %BF, and energy balance, <em>free</em> T(3) was a negative predictor of 24-h respiratory quotient (P < 0.05) and a positive predictor of 24-h lipid oxidation rate (P = 0.006). Prospectively, after an average follow-up of 4 +/- 2 y, the mean increase in weight was 3 +/- 9 kg. Baseline T(3) concentrations were associated with absolute and annual percentage of changes in weight (r = -0.27, P = 0.02, and r = -0.28, P = 0.009, for the age- and sex-adjusted associations, respectively).

CONCLUSIONS

In euthyroid Pima Indians, lower free T(3) but not free T(4) concentrations were an independent predictor of SMR and lipid oxidation and a predictor of weight gain. This finding indicates that control of T(4)-to-T(3) conversion may play a role in body weight regulation.

In recent years, some epidemiologic studies have suggested that extremely low frequency magnetic and electric fields might affect human health, and, in particular, that the incidence of certain types of cancer, depression, and miscarriage might increase among individuals living or working in environments exposed to such fields. Work in our laboratory studies whether and how changes in the electromagnetic environment might affect human health. The study presented here was designed to look for possible effects of acute exposure to 50-Hz linearly polarized magnetic fields (10 microT) on the hormones of the hypothalamic-pituitary-thyroid and hypothalamic-pituitary-adrenal axes. Thirty-two young men (20-30 years old) were divided into two groups (sham-exposed or control group, and exposed group) of 16 subjects each. All subjects participated in two 24-hour experiments to evaluate the effects of both continuous and intermittent (one hour "off" and one hour "on" with the field switched "on" and "off" every 15 seconds) exposure to linearly polarized magnetic fields. The subjects were exposed to the magnetic field (generated by three Helmholtz coils per bed) from 2300 to 0800 while recumbent. Blood samples were collected during each session at 3 hour intervals from 1100 to 2000 and hourly from 2200 to 0800. Total urine was collected every 3 hours from 0800 to 2300 and then again at 0800. No significant differences were observed between sham-exposed and exposed men for any of the parameters measured: thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, triiodothyronine, thyroxine, free triiodothyronine, free thyroxine, thyroxine-binding globulin, cortisol, 17-hydroxycorticosteroids (17-OH-CS) and TBK. These results suggest that acute exposure to either continuous or intermittent 50-Hz linearly polarized magnetic fields of 10 microT does not affect, at least under our experimental conditions, these endocrine functions or their circadian rhythmicity in healthy young men.

OBJECTIVE

Ghrelin promotes a positive energy balance, e.g. by increasing food intake. Stimulation of the activity of the hypothalamus-pituitary-thyroid (HPT) axis promotes a negative energy balance, e.g. by increasing energy expenditure. We therefore hypothesized that ghrelin suppresses the HPT axis in humans, counteracting its energy-saving effect.

METHODS

In this single-blind, randomized, cross-over study, we determined secretion patterns of free triiodothyronine (fT(3)), free thyroxine (fT(4)), TSH, and thyroid-binding globulin (TBG) between 2000 and 0700 h in 20 healthy adults (10 males and 10 females, 25.3+/-2.7 years) receiving 50 microg ghrelin or placebo at 2200, 2300, 0000, and 0100 h.

RESULTS

FT(4) plasma levels were significantly higher after ghrelin administration than after placebo administration from 0000 h until 0620 h except for the time points at 0100, 0520, and 0600 h. TSH plasma levels were significantly lower from 0200 until the end of the study at 0700 h except for the time points at 0540, 0600, and 0620 h. The relative increase of fT(4) (area under the curve (AUC) 0130-0700 h (ng/dl x min): placebo: 1.31+/-0.03; ghrelin: 1.39+/-0.03; P=0.001) was much weaker than the relative decrease of TSH (AUC 0130-0700 h (mIU/ml x min): placebo: 1.74+/-0.12; ghrelin: 1.32+/-0.12; P=0.007). FT(3) and TBG were not affected.

CONCLUSIONS

This is the first study to report that ghrelin affects the HPT axis in humans. The early fT(4) increase was possibly induced by direct ghrelin action on the thyroid where ghrelin receptors have been identified. The TSH decrease might have been caused by ghrelin-mediated inhibition at hypothalamic level by feedback inhibition through fT(4), or both.

Thyroid hormones are known to be essential for growth, development and metabolism. Recently mutations in the SLC16A2 gene coding for the monocarboxylate thyroid hormone transporter 8, MCT8, have been associated with Allan-Herndon-Dudley syndrome (AHDS), an X-linked condition characterized by severe mental retardation, dysarthria, athetoid movements, muscle hypoplasia and spastic paraplegia. Here we describe in detail the clinical and biochemical features in a boy affected by AHDS with severe neurological abnormalities and a novel de novo SLC16A2 gene insertion, 1343-1344insGCCC, resulting in a truncated protein lacking the last four transmembrane domains (TMDs) as well as the carboxyl cytoplasmic end. He presents mental retardation, axial hypotonia, hypertonia of arms and legs, paroxysmal dyskinesias, seizures. The endocrine phenotype showed low serum total and free thyroxine (T4), very elevated total and free triiodothyronine (T3) and normal thyrotropin (TSH) with blunted response to thyrotropin-releasing hormone (TRH). The latter finding was unexpected and suggested that the lack of functional MCT8 was counterbalanced at the thyrotrope cell level by high serum T3 concentration and/or by increased intrapituitary type 2 deiodinase (D2) activity. Our case constitutes a relevant contribution to better characterize this disorder and to elucidate the functional consequences of SLC16A2 gene mutations.

Up to 14% of Asian and 29% of African elephants in captivity are not cycling normally or exhibit irregular cycles based on progestin profiles. To determine if ovarian acyclicity is related to other disruptions in endocrine activity, serum pituitary, thyroid, adrenal, and ovarian hormones in weekly samples collected for 6-25 months were compared between normal cycling (n=22 each species) and non-cycling (n=6 Asian; n=30 African) elephants. A subset of cycling females (n=4 Asian, 7 African) also were blood sampled daily during the follicular phase to characterize the peri-ovulatory period. In normal cycling females, two leutinizing hormone (LH) surges were observed 3 weeks apart during a normal follicular phase, with the second inducing ovulation (ovLH). Serum FSH concentrations were highest at the beginning of the non-luteal phase, declining to nadir concentrations within 4 days of the ovLH surge. FSH remained low until after the ovLH surge and then increased during the luteal phase. A species difference was noted in prolactin secretion. In the African elephant, prolactin was increased during the follicular phase, but in Asian elephants concentrations remained stable throughout the cycle. Patterns of thyroid hormones (thyroid-stimulating hormone, TSH; free and total thyroxine, T4; free and total triiodothyronine, T3) and cortisol secretion were not affected by estrous cycle stage or season in cycling elephants. In non-cycling elephants, there were no fluctuating patterns of LH, FSH, or prolactin secretion. Overall mean concentrations of all hormones were similar to those in cycling animals, with the exception of FSH, prolactin, and estradiol. Mean serum FSH concentrations were lower due to females not exhibiting normal cyclic increases, whereas serum estradiol was higher overall in most acyclic females. Prolactin concentrations were significantly increased in 11 of 30 non-cycling females, all of which were African elephants. In sum, while there were no consistent endocrine anomalies associated with ovarian acyclicity, hyperprolactinemia may be one cause of ovarian dysfunction. The finding of elevated estrogens in some acyclic females also deserves further investigation, especially determining how it relates to reproductive tract pathologies.