We retrospectively evaluated the characteristics of adult patients admitted with thyrotoxic hypokalaemic periodic paralysis in Hong Kong. From 1984 to 1993, 45 Chinese adult patients were admitted with acute limb weakness, plasma potassium < or = 3.5 mmol/l and thyrotoxicosis confirmed by laboratory investigations. All but one were male. Seventy-five percent of attacks occurred between 9pm and 9am. Half of the attacks occurred between July and October (49.1%), most commonly in August (20%). Mean (+/- SEM) plasma potassium on admission was 2.17 +/- 0.08 mmol/l (range 1.1-3.5). In 15 episodes (27.3%), plasma potassium on recovery exceeded 5.0 mmol/l, while in three episodes (5.5%), potassium exceeded 6.0 mmol/l. No patient had a positive family history of thyrotoxic periodic paralysis. Only 28.9% had a known history of thyrotoxicosis before their first presentation with periodic paralysis. Twenty-seven (60%) had clinical evidence of thyrotoxicosis. Although all were biochemically thyrotoxic, 11.4% had only a mild degree of thyrotoxicosis (suppressed thyroid-stimulating hormone, high free thyroxine, but normal free triiodothyronine). One quarter of the patients had a normal erythrocyte zinc concentration, indicating either a short history of thyrotoxicosis or transient thyrotoxicosis. The diagnosis of thyrotoxic hypokalaemic paralysis should always be considered in Chinese patients with acute muscle weakness, especially in young males. Absence of clinical thyrotoxicosis does not exclude the diagnosis. Plasma potassium should be monitored carefully during treatment to prevent rebound hyperkalaemia.

No consistent data are present in literature about the effectiveness of levothyroxine (L-T4) liquid formulation in patients without malabsorption. The aim of this study is to compare the effectiveness of L-T4 liquid formulation, with L-T4 tablets, in hypothyroid patients without malabsorption or drug interference. One hundred and fifty two patients were recruited. Patients were switched from the L-T4 therapy in tablets, to liquid L-T4 at the same dosage, 30 min before breakfast. Serum thyrotropic hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were re-evaluated after 1-3 months (first control) and 5-7 months (second control) from the switch. TSH values significantly declined with respect to the basal value after the switch to liquid L-T4 both at the first control (P < 0.05) and at the second control (P < 0.01); FT4 and FT3 levels were not significantly changed. We show that liquid L-T4 is more effective than L-T4 tablet in controlling TSH levels in hypothyroid patients without malabsorption, gastric disorders, or drug interference.

BACKGROUND

Obesity is associated with a chronic low-grade inflammation. High-mobility group box 1 protein (HMGB1) plays a key role in inflammation and immunostimulatory and chemotactic processes. The aim of the study was to assess the role of HMGB1 in obese children and to evaluate its diagnostic profile in identifying childhood obesity-related complications, such as the metabolic syndrome (MS).

METHODS

Sixty obese children were enrolled and compared with 40 healthy children (control). Homeostasis model assessment of insulin resistance (HOMA-IR), lipid profile, thyroid hormones, and pro- and anti-inflammatory peptides such as C-reactive protein (CRP), adiponectin, interleukin 6 (IL6), IL18, IL23, TNFα, resistin, and HMGB1 were evaluated. Receiver operating characteristics (ROC) analysis was employed to calculate the area under the curve (AUC) for HMGB1, IL6, and adiponectin to find the best cutoff values capable of identifying MS in obese children.

RESULTS

HMGB1 levels were statistically higher in obese patients than in the control group (19.4±6.8 vs 3.7±1.2 ng/ml; P<0.0001). In obese patients, IL18, IL6, and resistin levels were significantly high, while adiponectin levels were low. At multivariate analysis, HMGB1 was found to be independently correlated with BMI, IL23, IL6, free triiodothyronine, HDL, and HOMA-IR. At ROC analysis, HMGB1 showed higher sensitivity and specificity (AUC, 0. 992; sensitivity, 94.7%; specificity, 97.5%) than IL6 and adiponectin in identifying MS in obese children.

CONCLUSIONS

HMGB1 plays an important role in the inflammatory process associated with childhood obesity. This peptide may be an important diagnostic marker for obesity-related complications, such as MS.

BACKGROUND

Maternal thyroid disorders during early pregnancy can influence pregnancy outcome and fetal development. The recent Endocrine Society Clinical Practice Guideline recommends a case-finding approach in which pregnant women who are at high risk for developing thyroid disease are tested.

OBJECTIVE

The purpose of this study was to use the first trimester-specific reference intervals of thyroid-related hormones to explore the prevalence of thyroid dysfunction during early pregnancy and to analyze effectiveness of different screening strategies.

METHODS

A multicenter cohort study.

METHODS

A total of 2899 pregnant women were enrolled in this study during their first trimester of gestation. Levels of TSH, free thyroxine, free triiodothyronine, and thyroid peroxidase antibodies (TPOAb) were measured and thyroid disorders of pregnant women were diagnosed based on the first trimester-specific reference intervals.

RESULTS

The prevalence of hypothyroidism was significantly higher in the high-risk group than in the non-high-risk group (10.9 vs 7.0%, χ²=7.1, P = 0.008). The prevalence of hyperthyroidism was not significantly different between the high-risk group and the non-high-risk group (2.7 vs 1.6%, χ²=2.27, P=0.13). Elevated levels of TPOAb and a personal history of thyroid disease increased the risk of thyroid dysfunction.

CONCLUSIONS

A case-finding strategy for screening thyroid function in the high-risk group would miss about 81.6% pregnant women with hypothyroidism and 80.4% pregnant women with hyperthyroidism.

BACKGROUND

Thyroid function depends on the essential trace mineral selenium, which is at the active center of the iodothyronine deiodinase enzymes that catalyze the conversion of the prohormone thyroxine (T(4)) to the active form of thyroid hormone, triiodothyronine (T(3)).

OBJECTIVE

Because selenium intake in the United Kingdom has fallen during the past 25 y, we wanted to determine whether current selenium status might be limiting conversion of T(4) to T(3) in the elderly, in whom marginal hypothyroidism is relatively common.

METHODS

We investigated the effect of selenium supplementation in a double-blind, placebo-controlled trial in 501 elderly UK volunteers. Similar numbers of men and women from each of 3 age groups, 60-64 y, 65-69 y, and 70-74 y, were randomly allocated to receive 100, 200, or 300 microg Se/d as high-selenium yeast or placebo yeast for 6 mo. As part of the study, plasma selenium, thyroid-stimulating hormone, and total and free T(3) and T(4) were measured. Data from 368 euthyroid volunteers who provided blood samples at baseline and 6 mo were analyzed.

RESULTS

Although selenium status at baseline correlated weakly with free T(4) (r = -0.19, P < 0.001) and with the ratio of free T(3) to free T(4) (r = 0.12, P = 0.02), we found no evidence of any effect of selenium supplementation on thyroid function, despite significant increases in plasma selenium. However, baseline plasma selenium in our study (x: 91 microg/L) was somewhat higher than in previous supplementation studies in which apparently beneficial effects were seen.

CONCLUSIONS

We found no indication for increasing selenium intake to benefit T(4) to T(3) conversion in the elderly UK population.

OBJECTIVE

To study the expression, distribution, and function of thyroid-stimulating hormone receptor (TSHR) and thyroid hormone receptors (TR) α1, α2, and β1 in human endometrium.

METHODS

Experimental clinical study.

METHODS

University hospital.

METHODS

31 fertile women.

METHODS

Endometrial biopsy samples obtained throughout the menstrual cycle.

METHODS

Real-time reverse transcriptase polymerase chain reaction, immunohistochemistry and Western blot to study the expression of TSHR, TRα1, TRα2, and TRβ1 messenger RNA (mRNA) and proteins in human endometrium.

RESULTS

We found TSHR, TRα1, TRα2 and TRβ1 mRNA and proteins expressed in human endometrium. Immunostaining for TSHR in the luminal epithelium and TRα1 and β1 in the glandular and luminal epithelium increased statistically significantly on luteinizing hormone (LH) days 6 to 9, coinciding with appearance of pinopodes. Endometrial stromal and Ishikawa cells expressed mRNA for TSHR, TR, and iodothyronine deiodinases 1-3. After 48 hours, TSH significantly increased leukemia inhibitory factor (LIF) and LIF receptor (LIFR) messenger RNA (mRNA) in endometrial stromal cells, but decreased their expression in Ishikawa cells. Glucose transporter 1 mRNA was up-regulated by TSH in Ishikawa cells. We found that TSH statistically significantly increased secretion of free triiodothyronine (T3) and total thyroxin (T4) by Ishikawa cells compared with nonstimulated cells.

CONCLUSIONS

Thyroid hormones are directly involved in endometrial physiology.

To investigate further the alterations in pituitary-thyroid function seen during starvation, we have measured basal and TRH-stimulated serum levels of thyrotropin (TSH), prolactin (PRL), growth hormone, thyroxine (T4), triiodothyronine (T3), free T4, free T3, and reverse T3 during prolonged fasting in seven obese men. Fasting was associated with a significant decrease in serum (4, (3, and free T3, while there was an increase in serum reverse T3; these values tended to return toward pre-fast levels as the fast continued beyond 3 weeks. No significant changes were seen in basal serum TSH, PRL, growth hormone, or free T4. Although the TSH response to TRH was diminished during fasting, PRL, T4, and T3 responses were unchanged. In addition to transient alterations in the peripheral metabolism of T4, these findings suggest that alterations in the thyroid hormone binding capacity of serum carrier proteins may occur during fasting. The blunted TSH response to TRH despite reduction of serum T3 concentration suggests that subtle alterations in hypothalamic-pituitary function may also occur.

Thyroid volume (ThV) and echogenicity by ultrasound were estimated in 324 schoolchildren (aged between 10 and 13-years) from high nitrate area (HNA) located in agricultural lowland with high nitrate drinking water supply (51-274 mg/l) from shallow wells. The data were compared to children of the same age from low nitrate area (LNA) consisting of 168 children from the neighboring area with very low nitrate (< 2 mg/l) drinking water and of 596 children from the city of Kosice located in a vicinity of LNA and also supplied by low nitrate water. Blood samples were obtained from 315 willing children from HNA and 109 children from LNA and the levels of thyrotropin (TSH), total thyroxine (TT4), free triiodothyronine (FT3) and thyroperoxidase antibodies (anti-TPO) in serum were determined. ThV (mean +/- SE) in 10-year (5.10 +/- 0.14 ml) and 13-year (5.97 +/- 0.11 ml) old children from HNA was significantly higher than that in two groups of respective age from LNA, 4.58 +/- 0.17 (p < 0.02) and 5.23 +/- 0.15 ml (p < 0.05), and from the city of Kosice, 4.77 +/- 0.10 ml (p < 0.05) and 4.87 +/- 0.1 0ml (p < 0.0001). The frequency of hypoechogenicity in HNA was also significantly higher than that in pooled LNA plus Kosice, 13.7% vs. 4.7% (p < 0.01) in 10-year and 10.6% vs. 5.7% (p < 0.03) in 13-year, respectively. The frequency of TSH level in the range of subclinical hypothyroidism >> 4.0 mU/l) in pooled age groups from HNA was 13/324 (4.0%) and that of positive anti-TPO was 8/324 (2.5%), while no case of either increased TSH or positive anti-TPO was found in 109 children from LNA. Finally, no differences in the levels of TT4 and FT3 were found between HNA and LNA. It was concluded that long-term exposure to high nitrate intake by drinking water and home made meals from local products results in increased thyroid volume and increased frequency of signs of subclinical thyroid disorders (thyroid hypoechogenicity by ultrasound, increased TSH level and positive anti-TPO).

Polybrominated diphenyl ethers (PBDEs) causing thyroidal effects have been demonstrated in in vivo and in vitro studies. PBDEs with structural similarities to thyroid hormones have increased recently, but the health effects for thyroid hormones have not been well studied. The study aimed to determine PBDE levels in cord blood and further to explore associations between prenatal PBDE exposures and thyroid hormones in cord blood. Fifty-four cord blood samples were collected after delivery. Cord-blood levels of BDE-15, 28, 47, 99, 100, 153, 154, and 183 were analyzed using a high resolution gas chromatograph with a high resolution mass spectrometer. Thyroid hormones were determined by an automated chemiluminescence analyzer. The mean, median, and standard deviation of ΣPBDEs were 4.72, 3.49, and 6.36 ng/g lipid, respectively. To adjust for confounding by maternal age, pre-pregnant BMI and gestational age, stepwise multiple linear regression was used after log(2) transformation of the exposure variables. A doubling of BDE-154 was associated with 0.043 ng/mL lower triiodothyronine (T3) values (adjusted r=-0.245, p=0.043). Likewise a doubling of BDE-153 was associated with 0.143 ng/mL lower free T3 (FT3) values and a doubling of BDE-183 with 0.084 ng/mL lower FT3 values (adjusted r=-0.487, p=0.023). In contrast, the T4 (thyroxine)/T3 ratio increased by 4.93 (adjusted r=0.277, p=0.017) when doubling BDE-100 exposure. No significant associations with BDE-47 or any other of the PBDEs was found. Our findings of an inverse relationship between BDE-153, BDE-154 or BDE-184 and thyroid hormones confirm the results of animal experiments but are in contrast to most epidemiological studies.

OBJECTIVE

Subclinical or frank hypothyroidism is causally implicated in endothelial dysfunction. Since the plasma concentration of the active form of thyroid hormone, triiodothyronine (T₃), is reduced in chronic kidney disease (CKD), where endothelial function is frequently altered, low T₃ may be a factor implicated in this disturbance in CKD patients.

METHODS

We investigated the relationship between flow-mediated vasodilatation (FMD) and thyroid hormones in a series of 217 nondiabetic patients with stage 3-4 CKD.

RESULTS

The plasma concentration of free T₃ (fT₃) was closely associated with FMD (r = 0.38; p < 0.001). fT₃ was also inversely associated with hemoglobin (r = -0.41; p < 0.001), systolic pressure (r = -0.28; p < 0.001) and the plasma concentration of the endogenous inhibitor of NO synthase, asymmetric dimethylarginine (ADMA; r = -0.18; p = 0.007). However, adjustment for ADMA markedly attenuated the fT₃-FMD link, a phenomenon suggesting that raised plasma ADMA, possibly driven by low fT₃, at least in part mediates the adverse effects of low T₃ on endothelial function in CKD.

CONCLUSIONS

Low T₃ in patients with moderate-to-severe CKD is a marker of endothelial dysfunction. This study sets a solid rationale for designing specific intervention studies aimed at clarifying the nature (causal or not causal) of the endothelial function-T₃ link in CKD.

The association of systemic lupus erythematosus (SLE) and thyroid autoimmunity has been reported by several studies in a wide range of variability. However, from a review of the literature, discrepant results have been reported. The aim of the study was to evaluate the prevalence of clinical and subclinical thyroid disorders in patients with SLE vs sex- and age-matched controls. Thyroid hormones and the presence of antithyroid antibodies were tested and thyroid ultrasonography was performed in 213 patients with SLE vs 426 sex- and age-matched controls, from the same geographic area, with a well-defined status of iodine intake. The odds ratio for subclinical hypothyroidism for female patients with SLE with respect to controls was 4.5 (95% confidence interval [CI], 2.5-8.4); for antithyroid peroxidase antibody (AbTPO) positivity, it was 2.6 (95% CI, 1.7-4.1); and for thyroid autoimmunity, it was 2.9 (95% CI, 2.0-4.4). The mean values of thyroid-stimulating hormone and AbTPO were higher in female SLE patients than in controls (P < .01). A significantly (P < .01) higher prevalence of clinical hypothyroidism and Graves disease was observed in female SLE patients than in controls. No significant difference between SLE patients and controls was detected with regard to free triiodothyronine and thyroxine. In our series, 3% of SLE patients had "nonthyroidal illness syndrome" vs 0 control. Thyroid function and AbTPOs should be tested and ultrasonography should be performed as part of the clinical profile in SLE patients. Subjects at high risk (women, positive AbTPOs, hypoechoic, and small thyroid) should have thyroid function follow-up and appropriate treatment in due course.

10 patients with a single hyperfunctioning thyroid nodule each were studied for pituitary thyrotropin (TSH) suppression. They were judged to be euthyroid on clinical grounds. The total thyroxine (T(4)D), free thyroxine (FT(4)), total triiodothyronine (T(3)D), and free triiodothyronine (FT(3)) were normal in most of the patients. Incorporation of (131)I into the hyperfunctioning thyroid nodules was not suppressed by the administration of physiological doses of T(3). Basal serum TSH concentrations were undetectable (<0.5 - 1.0 muU/ml) in all patients. The metabolic clearance of TSH in one patient before and after excision of the thyroid nodule was unchanged (40 vs. 42 ml/min) whereas the calculated production rate was undetectable before the operation (<29 mU/day) and normal after (103 mU/day). These data, in one patient, suggest that the undetectable concentration of TSH in these patients is a result of suppressed TSH secretion rather than accelerated TSH clearance. In eight patients, basal serum TSH concentrations failed to increase after the intravenous administration of 200 mug of thyrotropin-releasing hormone (TRH); minimal increases in serum TSH concentrations were observed in two patients. The suppression of TSH was evident despite "normal" concentrations of circulating thyroid hormones. The observation that normal serum concentrations of T(4)D, FT(4), T(3)D, and FT(3) may be associated with undetectable basal serum TSH concentrations and suppressed TSH response to TRH was also found in four hypothyroid patients given increasing doses of L-thyroxine and sequential TRH stimulation tests.

Mechanisms underlying thyroid hormone-induced changes in myocardial contractile state were investigated by studying the effects of triiodothyronine (T3) on Ca2+ fluxes across the sarcolemmal membrane and Ca2+ handling by the sarcoplasmic reticulum, using spontaneously contracting monolayers of cultured chick embryo ventricular cells. Cells were grown in serum-free medium containing either no T3 or 10(-8) M-T3 for 48 h. At [Ca2+]o levels of 0.6 and 1.2 mM, the velocity of cell contraction was significantly greater in cells grown in 10(-8) M-T3 than in its absence. At higher [Ca2+]o, no differences in the velocity of contraction were noted. 45Ca2+ exchange kinetic studies showed a biexponential pattern with a rapid and a slow component of uptake in cells grown both with and without 10(-8) M-T3. The rate of the rapid phase of uptake and total Ca2+ content were higher in cells grown in T3, with the increment in content ascribable to the rapidly exchangeable Ca2+ pool. Verapamil partially inhibited the T3-induced increase in the rapidly exchangeable pool. 45Ca2+ uptake in response to a step change to Na+-free medium in the presence of 1 microM-verapamil was significantly greater in cells grown in 10(-8) M-T3 than in T3-free medium. Cells grown in T3 showed 20% greater beating rate than cells grown in its absence. A similar increase in beating rate achieved by lowering [K+]o from 4.0 to 3.0 mM or by electrical stimulation failed to affect the rate of 45Ca2+ uptake or the size of the rapidly exchangeable pool; pacing-induced increases in rate resulted in reduction rather than augmentation of contractile state. Ca2+ efflux rate was greater in cells grown in 10(-8) M-T3 than in T3-free medium, whereas cells loaded with various levels of Ca2+ acutely by incubation at selected [Ca2+]o levels had similar efflux rates. Replacement of Na+ by choline in the efflux medium resulted in elevated Ca2+ efflux rates in cells grown both with and without T3; however, it remained greater in cells grown in 10(-8) M-T3 than in its absence. Caffeine (20 mM) in the efflux medium increased Ca2+ efflux to a greater degree in cells grown in T3 than without it. Caffeine also produced a greater tonic contraction in T3-treated cells than in cells grown in absence of T3 in Na+- and Ca2+-free medium.(ABSTRACT TRUNCATED AT 400 WORDS)

The nonproliferating chicken liver cell culture system described yields cell monolayers with morphological and lipogenic properties characteristic of the physiological-nutritional state of donor animals. Synthesis and secretion of fatty acid, cholesterol, and very low density lipoprotein (VLDL) occur at in vivo rates and respond to hormones and agents which affect these processes in vivo. Cells derived from fed chickens maintain high rates of synthesis of fatty acid and cholesterol for several days if insulin is present in the medium. High rates of fatty acid synthesis are correlated with the appearance of membrane-enclosed triglyceride-rich vesicles in the cytoplasm; deletion of insulin causes a decrease (T1/2 = 22 h) in fatty acid synthetic activity. Addition of glucagon or cyclic AMP (cAMP) causes an immediate cessation of fatty acid synthesis and blocks the appearance of the triglyceride-rich vesicles. Fatty acid synthesis in liver cells prepared from fasted chickens is less than 5% that of cells from fed animals. After 2-3 days in culture with serum-free medium containing insulin +/- triiodothyronine, fatty acid synthesis is restored to normal; glucagon or dibutyryl cAMP blocks this recovery. Liver cells derived from estradiol-treated chickens synthesize and secrete VLDL for at least 48 h in culture. Electron micrographs of these cells reveal more extensive development of the rough endoplasmic reticulum and Golgi complex compared to cells from untreated chickens. Whereas [3H]leucine incorporation into total protein is unaffected by estrogen treatment, [3H]leucine incorporation into cellular and secreted immunoprecipitable VLDL is markedly increased indicating specific activation of VLDL apopeptide synthesis; 8-10% of the labeled protein synthesized and secreted is VLDL. Dodecyl sulfate-acrylamide gel electrophoresis of immunoprecipitated 3H-VLDL reveals three major apopepetides of 300,000, 11,000, and 8,000 daltons corresponding to those of purified chicken VLDL.

The biochemical development of rotation-mediated aggregating brain cell cultures was studied in a serum-free chemically defined medium in the presence (complete medium) or the absence of triiodothyronine (T3). The expression of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) and myelin basic protein (MBP), two myelin components, was temporally dissociated in brain cell aggregating cultures grown in a complete medium. CNP increased from day 8 and reached a plateau around day 25. MBP accumulated rapidly from the third until the fourth week in culture. The total protein content increased gradually until day 25. The activity of ornithine decarboxylase (ODC) used as an index of cell growth and differentiation, showed two well-defined peaks of activity. The first peak reached a maximum at day 6 and correlated with both the highest DNA content and the peak of [3H]-thymidine incorporation. The second peak of ODC activity (from day 19 to 35) coincided with the differentiation of oligodendrocytes. These results confirm that aggregating fetal rat brain cells cultured in a serum-free chemically defined medium undergo extensive differentiation. Addition of T3 to the culture medium doubled the CNP activity by day 16. In contrast, MBP was only slightly increased by day 16, reaching at 25 and 35 days 8 to 10-fold higher values than the untreated cultures. When T3 was removed between day 16 and 25, CNP decreased almost to control values and MBP failed to accumulate. Moreover, when T3 was reintroduced into the medium (between day 25 and 35), CNP activity was restored and MBP content was partially corrected. T3 treatment produced a concentration-dependent increase in ODC activity which was observed only around day 19. The first peak of ODC activity observed at culture day 6 was independent of the presence of T3. These results obtained in brain cell cultures emphasize the direct effect of T3 on myelination.

In recent years, many authors have described several cases revealing an association between hyperthyroidism and pulmonary hypertension (PH). This observational study was designed to evaluate the incidence of PH in hyperthyroidism and was set in a department of internal medicine and pulmonary diseases with an out-patients department of endocrinology. Thirty-four patients, 25 women and nine men, with a mean age of 38 +/- 15 SD years participated. Twenty had Graves' disease and 14 had a nodular goitre. The patients were divided into two equally matched groups: those with a recently diagnosed hyperthyroidism, taking no drugs (group 1; n = 17) and those in a euthyroid state taking methimazole (group 2; n= 17). Transthoracic Doppler echocardiography was performed and systolic pulmonary artery pressurements of (PAPs) was determined by the tricuspid regurgitation method using the Bernoulli equation. Measurements of triiodothyronine, tetraiodothyronine, free thyroxine (Ft4), thyroid-stimulating hormone (TSH) and antithyroglobulin and antimicrosomal antibodies were also taken. We found a mild PH in seven patients of group 1 and in none of group 2. The mean +/- SD systolic pulmonaryartery pressurewas 28.88 +/- 6.41 in group 1 and 22.53 +/- 1.84 ingroup 2 (P<0.0001). A correlation was found between the TSH value and PAPs (r = -082;P < 0.001) and Ft4 and PAPs (r = 0 85; P < 0.001) in group 1. These findings indicate the presence of a frequent association between PH and hyperthyroidism. We suggest that hyperthyroidism be included in the differential diagnosis of PH.

Addition of sodium salicylate to human serum at concentrations often obtained during aspirin therapy causes 100-200% increases in free triiodothyronine (T(3)) and free thyroxine (T(4)) as estimated by ultrafiltration. The increase in free T(3) was unexpected since previous data had suggested that salicylate inhibits binding of T(4) only to thyroxine-binding prealbumin (TBPA) and that T(3) is not bound to this protein. Using ultrafiltration techniques, we demonstrated binding of T(3) to TBPA. The affinity constant for T(3)-TBPA binding appears to be slightly greater than that for albumin-T(3) binding. While salicylate inhibits the binding of T(3) (and T(4)) to TBPA, it can be predicted that little change will be observed in the free T(3) (or free T(4)) without inhibition of thyroid hormone binding to thyroxine-binding globulin (TBG). Using a competitive-binding protein displacement technique, it has been shown that sodium salicylate, like diphenylhydantoin (DPH), inhibits the binding of T(3) and T(4) to TBG. The magnitude of the increase in free T(3) and free T(4) induced by salicylates suggests that interference with TBG binding is its major effect. Aspirin was administered orally to two normal subjects in quantities sufficient to obtain serum salicylate levels of 20-25 mg/100 ml. This resulted in a decrease of 20-30% in total serum T(3) and T(4) levels. This decrease in T(4) levels is similar in magnitude to that previously observed in subjects receiving DPH. Unlike what has been observed with DPH treatment, therapeutic salicylate levels are associated with increases of 50-75% in the unbound fraction of both T(3) and T(4) which persist throughout an 8-10 day treatment period.

Subclinical hypothyroidism (SCH) is a common condition that is often observed without therapy. However, no evidence-based recommendation exists with regards to how patients with untreated SCH should be monitored. Monitoring involves regular assessment of symptoms and signs of hypothyroidism (HYPO) and biochemical tests of thyroid function. An important question when repeated tests of thyroid function are performed is how large a difference in test results is needed to be confident that the change is real and not just due to chance variation. Recent data show that the least significant difference between two tests in SCH is 40% for TSH and 15% for free thyroxine and free triiodothyronine, with 90% confidence. Furthermore, monitoring has to be based on biochemical function testing because serial evaluation of symptoms and signs related to HYPO is rather insensitive in detecting worsening of thyroid insufficiency. When the presence of thyroid peroxidase auto-antibodies (TPO-Ab) in serum has been demonstrated, repeated measurements do not add much useful information in the monitoring of individual subclinical hypothyroid patients, as levels of TPO-Ab vary in parallel with TSH in these patients. Lastly, we discuss how differences in the monitoring procedure influence the diagnostic outcome, and we suggest a follow-up approach for untreated subclinical hypothyroid patients.

We have previously demonstrated that at least four isoforms of protein kinase C (PKC; alpha, delta, epsilon, and zeta) are expressed in neonatal rat ventricular myocytes and that development is associated with a decline in their expression. The mechanism(s) regulating PKC isoform expression in ventricular myocytes is completely unknown. The developmental decline in PKC expression occurs, in large part, during the first 2 weeks of postnatal life, while thyroid hormone levels are known to be progressively increasing. Accordingly, this study examined the influence of thyroid hormone on PKC isoform expression to determine whether thyroid hormone can be implicated as a potential physiological regulator of PKC gene expression during normal cardiac development. Hypothyroidism was induced in adult rats by surgical thyroidectomy; thyroid status was manipulated in cultured neonatal ventricular myocytes by growth in serum-free medium with varying triiodothyronine (T3) levels. In each case, hypothyroidism was verified by a 10- to 50-fold increase in steady state mRNA for beta-myosin heavy chain. In hypothyroid adult ventricular myocardium, there was a selective 60% increase in the expression of PKC epsilon protein that corresponded to an increase in maximally stimulated PKC enzyme activity with PKC epsilon substrate peptide (epsilon pep) but not with histone as substrate. Northern blot analysis revealed a 70% increase in PKC epsilon mRNA, indicating that the regulatory effects of thyroid hormone are mediated, at least in part, at the message level. In neonatal ventricular myocytes, there was a T3-dependent reduction in immunoreactivity for both PKC alpha and PKC epsilon that was associated with significant reductions in both histone- and epsilon pep-kinase activities. The concentration of T3 that half-maximally repressed PKC alpha and PKC epsilon expression was approximately 0.5 nmol/L. Thyroid hormone had no effect on PKC delta and PKC zeta expression in neonatal or adult ventricular myocytes. PKC isoform expression in cardiac fibroblasts was not influenced by variations in the thyroid hormone concentration during culture. These results provide evidence that thyroid hormone specifically represses PKC alpha and PKC epsilon in the neonatal heart and PKC epsilon in the adult heart. Thyroid hormone-induced changes in PKC may play an important permissive role in the modulation of autonomic responsiveness in ventricular cardiomyocytes.

OBJECTIVE

To evaluate neuroendocrine changes in critical care patients with acute space occupying hemispheric stroke.

METHODS

22 patients with acute space occupying hemispheric stroke were studied (mean age 57.7 years; five women, 17 men). Plasma levels of prolactin, thyrotropin (TSH), total thyroxine (T4), free thyroxine (FT4), and total triiodothyronine (T3) were measured on admission and thereafter on days 3, 5, 7, and 9. Cortisol and ACTH levels were analysed at 8.00, 16.00, and 24.00 hours each day. A TRH stimulation test with measurements of TSH and prolactin was done on day 3.

RESULTS

Nine patients underwent decompressive craniectomy and nine were treated with moderate hypothermia. All patients received vasopressor drugs because of arterial hypotension. Plasma ACTH and cortisol values were abnormally low despite systemic hypotension and acute systemic illness, and remained low throughout the observation period. The diurnal rhythm of cortisol was not preserved. Prolactin levels increased during the observation period, and were well above normal on day 9. Thyroid function was slightly suppressed until day 7. TRH stimulation of plasma TSH and prolactin was low.

CONCLUSIONS

Patients with an acute space occupying cerebral infarct show profound neuroendocrine changes. The central regulation of adrenal and thyroid function and prolactin release is impaired, which may compromise the clinical course of affected patients and have implications for therapeutic management.

We measured serum total and free thyroxine (T4) and triiodothyronine (T3) concentrations, free T4 and T3 indexes, thyroid-stimulating hormone (TSH), thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) concentrations in 98 patients hospitalized for acute medical illnesses. The free thyroxine index (FT4I) or TSH level was abnormal in 16 percent, but only 3 percent had thyroid disease. Serum fre T4 measurements by equilibrium dialysis were abnormal in 25 percent, but no additional patients who initially had abnormal concentrations of serum free T4 were subsequently proved to have thyroid disease. Patients with supranormal serum free T4 concentrations (21 percent) ahd higher serum T4, lower serum T3, and higher serum reverse T3 (rT3) concentrations than other patients, but the measured changes in serum T4, TBG and TBPA levels could only partly account for the magnitude of the free T4 elevation. In these acutely ill patients, an accurate diagnosis of thyroid disease could be achieved by determination of FT4I and TSH level and a history of medication usage. We conclude that other tests are rarely necessary for this purpose in a patient population such as this.

BACKGROUND

Measurements of free thyroxine (FT4) and free triiodothyronine (FT3) are important for the diagnosis and monitoring of thyroid diseases. Considerable differences among methods limit their clinical utility, however, and accurate methods are needed for various clinical specimens. We describe a direct equilibrium dialysis (ED)-liquid chromatography (LC)/tandem mass spectrometry (MS/MS) method for FT4 and FT3.

METHODS

ED was selected as the separation step. Serum samples were dialyzed 1:1 against a simple protein-free buffer for 20 h at 37 degrees C. Thyroid hormones in dialysates were purified by online solid-phase extraction (SPE), then chromatographically separated and quantified in positive ion and multiple reaction monitoring modes.

RESULTS

For FT4 and FT3, the lower and upper limits of quantification were 1 ng/L (pg/mL) and 400 ng/L with total imprecision <10%. The method correlated well with an ED-RIA, 2 direct immunoassay methods for FT4, and 1 direct immunoassay and 1 tracer dialysis method for FT3. The adult reference intervals were 12.8-22.2 ng/L for FT4 and 3.62-6.75 ng/L for FT3. Reference intervals for the second trimester of pregnancy (14-20 weeks of gestation) were also established.

CONCLUSIONS

We developed a simple protein-free buffer and ED procedure. The performance characteristics and high throughput of the LC-MS/MS method with online SPE for FT4 and FT3 (also reverse T3) are sufficient for the intended clinical use.

Experimental studies suggest that polybrominated diphenyl ethers (PBDEs) can influence thyroid function, although the few human studies reported provide little support for this premise. Great Lakes sportfish anglers represent a population with potentially elevated dietary exposure to PBDEs due to the lipophilic nature of these compounds. Thirty-six licensed anglers who participated in the New York State Angler Cohort Study donated blood and completed questionnaires regarding demographic, clinical and sportfish consumption information. Archived blood specimens were analyzed for thyroid stimulating hormone, total and free thyroxine, total triiodothyronine, total serum lipids and nine PBDE congeners. PBDE congener profiles were dominated by BDE-47 (median=7.9ng/g lipids), BDE-153, and BDE-99 (medians=1.8ng/g lipids). No significant associations were observed between congeners, or their sum (ΣPBDEs), and thyroid function. However, the possibility of a positive association between ΣPBDEs and fT(4), detectable with an approximate ninefold increase in sample size, suggests that additional studies are needed.

This study investigated the relationships of steroid and thyroid hormones with total noncoplanar polychlorinated biphenyls (PCBs), total toxic equivalents (TEQs) from dioxins-like organochlorines, and dichlorodiphenyl dichloroethene (DDE) in 56 male frequent and infrequent Great Lakes sport caught fish consumers. Significant negative associations were found for triiodothyronine (T3), thyroxine (T4), thyroid stimulating hormone (TSH), and sex hormone binding globulin (SHBG)-bound testosterone with PCBs, for TSH with total TEQs, and for estrone sulfate with DDE, adjusting for age, body mass index, and medication use. Follicle-stimulating hormone, luteinizing hormone, free testosterone, and SHBG were not significantly associated with organochlorines. Models that accounted for exposure to both PCBs and TEQs predicted T4, estrone sulfate, and SHBG-bound testosterone better than models that included either PCBs or TEQs alone, with the lowest hormone levels occurring in the participants with both higher PCB levels and lower TEQ levels. These data suggest that exposure to PCBs, dioxin-like organochlorines, and DDE, alone and potentially in combination, may be associated with effects on the endocrine system in adult males. Further studies should help delineate specific exposure effects and effects of exposures to other common environmental contaminants alone and in combination with PCBs.