Two thyroid hormone response elements are present in the promoter of human thyroid hormone receptor beta 1

Autoregulation of the human thyroid hormone receptor beta 1 (hTR beta 1) promoter was assessed by chloramphenicol acetyltransferase and luciferase reporter assays of transient transfections into COS1 and GH3 cells, DNase I footprinting, and gel shift assays. A 5'-deletional analysis of the promoter showed that the region between -906 and -839 and the sequence from -438 to -130 were positively regulated by T3 in COS1 cells cotransfected with an hTR beta 1 expression vector. We also transfected deletion constructs into GH3 cells and showed similar effects of T3 on the trans-activation of the reporters. DNase I footprinting showed a protected inverted palindromic thyroid response element (TRE) at position -890 to -866 in the distal fragment and a direct repeat at position -190 to -166 in the proximal fragment, which were protected by TRs. Mutation of each TRE significantly decreased the trans-activation of the promoter by T3. Gel mobility shift assays showed both proximal and distal TREs formed a retarded band with hTR alpha 1 or hTR beta 1 expressed in COS1 cells and reticulocyte lysates. The bands formed on the distal TRE and the proximal TRE appear to be preferentially formed by a TR homodimer and a heterodimer, respectively. Furthermore, the band formed on the distal TRE disappeared after adding T3 but that on the proximal TRE did not. These results indicate that hTR beta 1 expression is directly regulated by hTR alpha 1, beta 1, and their ligand through two TREs. The different structure of the TREs in this promoter suggests their physiological role in transcriptional regulation may be different.

Formation of the adult rudiment of sea urchins is influenced by thyroid hormones

After the sea urchin embryo has developed to a pluteus larva, the adult rudiment (sea urchin rudiment) is formed, with other adult structures, on the left side of the larva and finally the juvenile sea urchin is formed after metamorphosis. We report here that thyroid hormones (THs) are involved in the formation of the adult rudiment and the adult-type skeleton and the resorption of larval tissues of the sea urchin. The contents of THs in the larval body were determined by radioimmunoassay after the separation of individual THs by HPLC. We confirmed the presence of THs in the larval body and in algae on which the larvae feed. The THs accumulate gradually following the development of the larva and reach maximum levels at the eight-armed stage when the adult rudiment is completed. These results suggest that the development of the larva is influenced by THs accumulated in the larval body. However, inhibitors for the synthesis of THs do not affect the development of the larval body, suggesting a supply of THs from algae.

Detection of thyroid hormones in human embryonic cavities during the first trimester of pregnancy

Transfer of maternal thyroxine (T4) to the human fetus near term has recently been demonstrated. We investigated whether maternal thyroid hormone is available to the conceptus during the first trimester of pregnancy as well. Transvaginal ultrasound-guided puncture of the embryonic cavities was performed during the first trimester of pregnancy to obtain coelomic fluid between 6 and 11 weeks, and amniotic fluid between 8 and 11 weeks of pregnancy. T4 was found in coelomic fluid with mean values (+/- SEM) being 961 +/- 193 pmol T4/L (747 +/- 150 pg/mL). Concentrations increased both with gestational age and with rising maternal serum T4. Concentrations of 3,5,3'-triiodothyronine (T3) were at least 30 times lower, and those of 3,3',5'-triiodothyronine (rT3) four times higher, than coelomic fluid T4. Thyroxine and rT3 in amniotic fluid (8-11 weeks) were markedly lower than in the coelomic fluid, and T3 was undetectable. These results show that maternal thyroxine can cross the placental barrier as early as the second month of pregnancy. T4 from the coelomic fluid may reach the embryo via the yolk sac. This finding raises the possibility that the increase in maternal T4 occurring during the first trimester may be functionally important for the developing embryo, when its thyroid is not yet functioning.

Thyroid hormones and putative nuclear T3 receptors in tissues of the ascidian, Phallusia mammillata cuvier

Thyroid hormones were measured by radioimmunoassay in blood plasma and in extracts (butanol/chloroform/ammonia) of pharynx, alimentary canal, and tunic of Phallusia mammillata. Other animals were injected with [125I]T3 and its distribution in the same tissues was determined from 6 to 48 hr after injection. Last, the saturable binding of [125I]T3 to salt-extracted nuclear proteins in the pharynx and alimentary canal was studied in vitro. T4 was found in all tissues examined and in the same order of magnitude (2.7 to 8.4 ng/g) whereas plasma concentration was low (0.2 ng/ml). Tissue T3 concentrations were always much lower than T4 tissue concentrations, being highest in alimentary canal (0.8-1.1 ng/g) and very low in the tunic as well as in plasma, in which T3 was generally below 0.02 ng/ml. The tissue distribution of [125I]T3 was correlated with T3 concentrations. Tissue/plasma ratios were approximately 10 in the alimentary canal, 5 in the pharynx, and 0.18 in the tunic. Saturable binding of T3 to nuclear proteins in the alimentary canal and pharynx was demonstrated. The affinity (Kd) was similar to that found in tissues from other chordates but the maximal binding capacity was much lower. The very low levels of plasma T3 and low T3/T4 ratios may indicate that the endostyle releases primarily T4 into the body fluid. On the other hand, the high levels of T3 and the high T3/T4 ratios in the alimentary canal suggest that this metabolically active target tissue is the main site of the process of deiodination of T4 into T3, a process which has been previously shown in P. mammillata in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of thyroid gland volume during the first 3 months of life in breast-fed versus iodine-supplemented and iodine-free formula-fed infants

The spontaneous development of thyroid gland volume (TGV) during the first 3 months of life was studied in entirely breast-fed infants (n = 21) and compared to those fed an iodine-supplemented formula (n = 19), an iodine-free formula (n = 5), or partially breast-fed in addition to an iodine-free (n = 4) or an iodine-supplemented formula (n = 16). The TGV of the infants and their mothers was determined sonographically in addition to their urinary iodine concentrations 5-7 days postpartum and 3 months later. In ten additional lactating mothers the breast milk concentrations of thyroid hormones and iodine were determined. It was shown that at 3 months of age an infant consuming about 1000 ml breast milk per day receives about 2 micrograms thyroid hormones and 55 micrograms iodine per day. At the end of their first week of life the infants showed a TGV between 0.28 and 1.5 ml (median 0.61 ml) and a urinary iodine concentration between 0.03 and 16.3 micrograms/dl (median 3.0 micrograms/dl). At 3 months of age the TGV of the breast-fed infants had decreased by a median of 0.24 ml (= -34%; median of percentage changes) whereas those fed a formula without iodine had increased by a median of 0.26 ml (= +50%; median of percentage changes). Those receiving an iodine-supplemented formula showed a TGV reduction of 0.14 ml (= +2%; median of percentage changes). The TGV development of the partially breast-fed infants lay between those being exclusively breast or formula fed.(ABSTRACT TRUNCATED AT 250 WORDS)

Hashimoto's thyroiditis in HTLV-I carriers

We describe two HTLV-I virus carriers who have biopsy-proven Hashimoto's thyroiditis. The first patient, a 64-year-old female, has had goiter and hypothyroidism since the age of 56. The second patient, a 66-year-old male, developed hyperthyroidism and goiter at the age of 44, but at present he is hypothyroid. Both patients are positive for anti-thyroid antibodies and anti-HTLV-I virus antibody. Findings of the thyroid biopsy specimens were consistent with Hashimoto's thyroiditis. These data suggest that Hashimoto's thyroiditis develops in HTLV-I carriers who have no clinical evidence of HAM/TSP.

The Anagen system for automated fluorometric immunoassay

We describe a new discrete microprocessor-controlled analyzer, the AN2000, which fully automates fluorometric immunoassays by using a magnetic separation of the solid phase and an alkaline phosphatase label. It can operate in random-access or batch mode with a dwell time typically less than 20 min. The analysis rate is 75 samples per hour and the system can hold refrigerated reagents for as many as 20 different analytes. The substrate and wash buffer are common to all analytes. The system can hold as many as 80 samples at once. The operator can select from the menu-driven operator interface any combination of the available analytes to be run for each sample, using either the touch screen or the keyboard. Results are calculated from a stored calibration curve that is stable for greater than or equal to 1 month. The AN2000 is capable of automating most assay formats because the available timings, volumes, incubations, and wash cycles can be used in any combination.

Fine needle aspiration biopsy--a critical investigation in thyrotoxicosis

Four hundred and fifty two patients having clinical features of thyrotoxicosis have been studied for their hormonal (T4, T3 and TSH) content, I131 uptake levels and FNAB at repeated intervals. Four hundred and twenty seven had presented with diffuse enlargement and rest 25 cases with nodular enlargements. Of the primary hyperthyroidism cases 342 (82.4%) were of Grave's disease without exophthalmos and 73 (17.6%) with exophthalmos. T4, T3 and I131 uptake levels have correlated well with the degree of morphological changes as observed on FNAB. Degree of nuclear pleomorphism has correlated well with the duration of disease. Critical evaluation of morphological changes on FNAB has been done in all cases of primary hyperthyroidism being treated with neomercazole and radioactive iodine therapy. Treatment with neomercazole had shown, good correlation between time lag and the retrogressive changes. This was not so in cases treated with radioactive iodine therapy. Various known complications of radioactive treatment e.g. development of hypothyroidism, refractory and recurrent hyperthyroidism, exacerbation of the disease, radiation thyroiditis, and severe degree of dysplastic changes could be demonstrated in some cases on serial aspirations.

Method for the quantitation of iodothyronines in body tissues and fluids using high-performance liquid chromatography

The separation and quantitation of iodotyrosines and iodothyronines [3-monoiodo-L-tyrosine, 3,5-diiodo-L-tyrosine, 3,5-, 3,3' and 3',5'-diiodo-L-tyronines, 3,5,3'-triiodo-L-thyronine (T3), reverse 3,3',5'-triiodo-L-thyronine and 3,3',5,5'-tetraiodo-L-thyronine (T4)] from animal tissues (brain, liver and serum) by a new high-performance liquid chromatographic (HPLC) method is described. Rats were infused with iso-osmotic sodium chloride containing 100 microM phloretin to block deiodination. The tissues were extracted using differential pH values to separate other amines from the amine containing iodothyroid hormones. Aliquots of tissue extracts (25-100 microliters) were reacted overnight with 5-dimethylaminonaphthalene-1-sulfonyl chloride and their iodotyrosine and iodothyronine content determined by HPLC utilizing fluorimetric detection. Resolution of the individual compound peaks was achieved by gradient elution with a 3.0 mM H3PO4 buffer. Greater sensitivity has been achieved (less than 1.0 pmol/g) utilizing fluorescence rather than ultraviolet absorbance for the quantitation of these iodinated compounds. The method is superior also to other methods in that recoveries, based on those of 125I-labelled T4 and T3, were 89-97%.

The pituitary gland in hyperthyroidism

The pituitary glands of 33 patients (24 women and 9 men, 18 to 78 years old) who died in thyrotoxicosis (18 with Graves' disease and 15 with toxic multinodular goiter [Plummer's disease]) were examined by histologic and immunocytologic methods. Thirteen patients (39%) died in "thyroid storm." The avidin-biotin-peroxidase complex immunostaining method was used to demonstrate the spectrum of pituitary hormones, including growth hormone, prolactin, adrenocorticotropic hormone, thyrotropin, follicle-stimulating hormone, luteinizing hormone, and alpha-subunit. The most striking finding was a pronounced decrease or loss of immunoreactivity to thyrotropin in all thyrotoxic cases, a consistent change that allowed ready distinction of thyrotoxic from euthyroid pituitary glands. When immunoreactive thyrotrophs were identified, they were sparse and small and demonstrated only faint thyrotropin reactivity. No morphologic differences were noted between the pituitary glands of patients with Graves' disease or Plummer's disease or between sexes. Loss of thyrotropin immunoreactivity was found to be reversible in that thyrotropic cells in the pituitary glands of 16 additional concurrently studied patients, who had thyrotoxicosis but were treated and subsequently had normal thyroid function or hypothyroidism, appeared normal or even hyperplastic. Other types of adenohypophysial cells in both the thyrotoxic and the successfully treated groups exhibited no abnormalities. Pituitary adenomas were incidental findings in 6 of the 33 patients (18%). Their immunotypic spectrum included three prolactin-immunoreactive tumors, two growth hormone-containing adenomas (one of which was plurihormonal), and one tumor with follicle-stimulating hormone and luteinizing hormone; no thyrotropin-containing adenomas were noted. No examples of pituitary hyperplasia were encountered in pituitary glands of thyrotoxic patients, and no hypophysitis or fibrosis was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of tilapia thyrotropin from a crude pituitary homogenate by immunoaffinity chromatography using a matrix of antibodies against porcine follicle-stimulating hormone

An immunoadsorbent matrix using antibodies against porcine follicle-stimulating hormone (pFSH), a high heterothyrotropic stimulant in tilapia, was used to purify tilapia thyrotropic hormone (t-TSH) from crude pituitary extracts. A homologous bioassay monitored TSH bioactivity during the purification. Thyroid hormones (thyroxine, T4; triiodothyronine, T3; and reverse triiodothyronine, rT3) and testosterone were measured in vivo in Tilapia nilotica. TSH activity eluted as one major peak at pH 2.8 using a PBS-glycine buffer. The TSH fraction increased plasma T4 and plasma rT3. The potency of tTSH was comparable to that of pituitary extract or its Con A II fraction; however, pFSH was a stronger thyroid stimulant. tTSH had no effect on plasma T3 levels and was free of gonadotropic activity, as indicated by its failure to alter plasma testosterone concentrations. Chromatographic and electrophoretic analyses demonstrated a high degree of purity. Like other vertebrate TSHs, the tTSH appeared to have a subunit structure with a possible microgeneity in one subunit.

Hormonal patterns in a successful pregnancy of a patient with late-onset 21-OH deficiency taking methylprednisolone; a case report

A successful pregnancy of a young woman with late-onset congenital adrenal hyperplasia (LOCAH) is reported. Exogenous glucocorticoids are the most commonly used regimen in such cases both for suppression of adrenal overstimulation and avoiding masculinization of a female fetus. In our LOCAH patient methylprednisolone has been used for treatment. We present the management and the outcome of this pregnancy, as well as the hormonal follow-up.

Comparison of high-performance liquid chromatographic detection methods for thyronine and tyrosine residues in toxicological studies of the thyroid

Four high-performance liquid chromatographic methods for the detection of thyroid hormones (iodinated thyronines) and precursors (iodinated tyrosines) have been developed and evaluated. Two methods consist of direct determination of the parent compounds with detection at ultraviolet wavelength (230 nm) and with electrochemical detection. The two other methods consist of a pre-column derivatization (with fluorenylmethyl chloroformate and dabsyl chloride) prior to high-performance liquid chromatographic analysis. The various methods were evaluated based on their practical use and sensitivity. The method with direct ultraviolet detection turned out to be the most practical method. With this method analyses of thyroid homogenates have been performed from rats from a toxicological experiment.

Evidence from dwarf rats that growth hormone may not regulate the sexual differentiation of liver cytochrome P450 enzymes and steroid 5 alpha-reductase

Differences in the pattern of growth hormone (GH) secretion in mature rats (i.e., "continuous" secretion in females versus "pulsatile" secretion in males) are thought to be the underlying cause of sex-dependent differences in a subpopulation of liver microsomal P450 enzymes and steroid 5 alpha-reductase. A new strain of dwarf rats (NIMR/AS) has recently been shown to have low or undetectable levels of circulating GH due to a selective defect in pituitary GH synthesis. We have measured the levels and/or activity of IIA1 (P450a), IIA2 (P450m), IIC11 (P450h), IIC12 (P450i), IIIA2 (a P450p isozyme), and steroid 5 alpha-reductase in liver microsomes from male and female dwarf rats, to test the hypothesis that the expression of these sexually dimorphic enzymes is regulated by GH. In mature rats, the levels of liver microsomal IIA2, IIC11, and IIIA2 were higher in male than in female dwarf rats, whereas the levels of activity of IIA1, IIC12, and steroid 5 alpha-reductase were greater in female than in male dwarf rats. These sex differences resulted from age-related changes in either male dwarf rats (i.e., an increase in IIC11 and IIA2 and a decrease in IIA1) or female dwarf rats (i.e., an increase in IIC12 and 5 alpha-reductase and a decrease in IIIA2). The magnitudes of these sex-dependent, age-related changes were essentially indistinguishable from those observed in normal rats. These unexpected results suggest that GH is not the pituitary factor responsible for regulating the levels of sexually dimorphic, steroid-metabolizing enzymes in rat liver. Alternatively, it is possible that these enzymes are regulated by extremely low levels of GH. In either case, the current model of how steroid-metabolizing enzymes are regulated in rats must be revised to account for the normal sexual differentiation of these enzymes in dwarf rats.

Thyroid function in patients with chronic headache

Headache is one of the neurological manifestations of hypothyroidism but it is unknown whether there is a relationship between hyperthyroidism and chronic headache. Thyroid function tests were performed in 30 patients with chronic headache. Six were found to have hyperthyroidism and none had hypothyroidism. Thyroid testing may be useful for differential diagnosis of chronic headache, and indicates that headache could be caused by hyperthyroidism.

Measurement of thyroid hormone in the rat thyroid gland by radioimmunoassay

The present paper describes (i) a hydrolysis technique with Pronase and leucine aminopeptidase using one rat thyroid gland, resulting in maximum release of thyroid hormones and minimum deiodination, and (ii) a simple and rapid procedure for thyroid hormone radioimmunoassays in thyroid hydrolysates using commercial kits intended for serum thyroid hormone determinations. The procedure is used to determine T4, T3, and rT3 concentrations and hormonal molar ratios in a thyroid gland from a male Wistar rat. The reliability of the method is also studied.

Superiority of the use of a pre-incubated complex of primary and second antibody in the radioimmunoassay of thyroid hormones

We report on the superiority of a radioimmunoassay (RIA) system wherein the second antibody (Ab2) is incorporated as a pre-incubated complex with the primary antibody (Ab1) for the assay of haptens like triiodothyronine (T3) and thyroxine (T4). Separation of the antibody bound and free antigen (Ag) was accomplished by 8% polyethylene glycol (PEG) (final concentration) following a single incubation of less than 1 h. The other advantages of this system are a 15-fold reduction in the quantity of Ab2 (without any need for increasing the concentration of PEG) and the consequent savings in cost.

[The effect of the duration of a weight reduction regimen on the hormonal, metabolic and cardiovascular response]

The rapid weight decrease at the beginning of strict slimming regimens leads often to an inconsiderate shortening of these cures. Our long-termed experience with a slimming regimen lasting 13 days and based on diet (3.7 MJ) and 4 hours of supervised exercise of low to moderate intensity was omitted by the organizers. They shortened the cure to 8 days. We checked therefore a group of obese women on the first, eighth and twelfth day in the course of this regimen. A statistically significant decrease of serum insulin, growth hormone, triiodothyronine and cholesterol was observed on the twelfth day. These trends were not significant on the eighth day. On the other hand, the step-test has shown on the eighth day a reduction of the heart rate during recovery. Nevertheless, a higher level of significance was obtained after a cure of 12 days. No significant response to the regimen was obtained in the case of blood glucose, thyroxine, cortisol, uric acid, AST and ALT. The advantages of the 12 day regimen were discussed--especially the decrease of insulinemia, because hyperinsulinemia is responsible for several complications of obesity. The importance of the decrease of cholesterolemia and the modification of heart rate after a load was also stressed. These favourable effects should not be depreciated by a smaller weight decrease on the second week due to an enhanced synthesis of proteins, stimulated by exercise and supported by a decrease of T3 which brings a protection against energy defficiency.

Low prevalence of thyrotropin receptor antibody in primary hypothyroidism in Japan

The prevalence of TSH receptor antibody (TRAb), measured by RRA assay (TSH-binding inhibitor immunoglobulin, TBII) and biological stimulation-blocking assay (thyroid-stimulation blocking antibody, TSBAb), was examined in 134 consecutive patients with primary hypothyroidism due to autoimmune thyroiditis [83 patients with goitrous Hashimoto's disease (group A) and 51 with primary atrophic hypothyroidism (group B)]. In group A, TBII was detected in 6 patients (7%), TSBAb in 7 (8%), and both in 4 (5%). Similarly, in group B, TBII was detected in 7 patients (14%), TSBAb in 7 (14%), and both in 5 (10%). TBII with TSBAb activity was low or moderate in group A, but strongly positive in group B. No relationship was apparent in either group between TBII or TSBAb activity and any clinical or laboratory parameter examined. Moreover, no clinical or laboratory findings distinguished patients with TRAb from those without. The low prevalence of TRAb in primary hypothyroidism suggests that intrathyroidal cell-mediated destructive mechanisms may be more important in the pathogenesis of hypothyroidism in autoimmune thyroiditis.

A simple method for the separation and quantitation of radiolabeled thyroid hormones in thyroxine clearance studies

A method was developed to facilitate the separation and quantitation of radiolabeled thyroxine in plasma for thyroxine clearance studies. Following intravenous injection of radioactive thyroxine, the radiolabeled thyroid hormones were isolated from plasma protein and polar metabolites by solid phase extraction on a C18 sorbent bed. The individual thyroid hormones were then separated by ion-pair reversed phase chromatography and sequentially eluted through a UV detector and radiochromatographic detector. The radioactivity of individual radiolabeled thyroid hormones was corrected for recovery of carrier as determined from UV absorbance. The recoveries of thyroxine and 3,5,3'-triiodothyronine (T3) were 96% and 101%, respectively.

Acute decrease in vitellogenin synthesis by deprivation of food and water in laying hens

Vitellogenin synthesis during a decrease in egg production caused by depriving food and water was investigated in Single Comb White Leghorn hens. They were transferred from long days of 14L: 10D to short days of 10L: 14D 5 days before food and water deprivation. Then food was deprived for 5 days and water for 2 days. The body weight was markedly decreased by the treatment and reached its minimum after 5 days. The egg production rate which was 85% before the treatment was nil after 4 days. On day 3 the circulating vitellogenin concentrations, measured by a newly established RIA system, was markedly decreased by deprivation of food and water to 22% of the pretreatment level. The concentrations remained less than 10% during cessation of egg laying. Serum luteinizing hormone (LH) and progesterone concentrations decreased gradually, but estradiol 17 beta (E2) decreased abruptly. This acute decrease closely coincided with the decrease in egg production and the weight of the oviduct and ovary. These concentrations were gradually increased after day 16 and returned to the normal level after 46 days. Circulating thyroxine (T4) and triiodothyronine (T3) concentrations gradually increased from the beginning of the change in the day length and peaked on day 7 or 9, whereas reverse (r)T3 rapidly increased. The concentrations again decreased at the beginning of molting which occurred later due to the deprivation of food and water. Thus, these results demonstrated for the first time that the decrease in egg production induced by deprivation of food and water closely related to the decrease in vitellogenin synthesis as well as gonadal and pituitary functions. Further, recovery of egg production was coupled with the increase in the ovary and oviduct weight, and circulating LH, E2, progesterone, and vitellogenin.

Erythrocyte zinc concentration in patients with subacute thyroiditis

We have recently reported that red blood cell (RBC) zinc (Zn) in patients with hyperthyroidism reflects a patient's integrated thyroid hormone level over the previous few months. In the present paper RBC Zn concentrations were measured in 10 patients with subacute thyroiditis whose total plasma T4 and T3 levels were elevated. The values were compared with those obtained in 10 patients with untreated Graves' disease, whose plasma T4 concentrations were elevated to the same level as in the former group. The RBC Zn concentration was normal in 9 of 10 patients with subacute thyroiditis, but was depressed in all patients with Graves' disease. The mean (+/- SE) RBC Zn in patients with subacute thyroiditis was 162 +/- 9 mumol/L, significantly (P less than 0.001) higher than that in Graves' disease (87 +/- 5 mumol/L). During prednisolone treatment the RBC Zn in patients with subacute thyroiditis remained at the normal level and did not change significantly, although it was slightly decreased at 2 and 4 weeks of treatment. On the other hand, the RBC Zn in patients with Graves' disease was significantly increased at 8 weeks of treatment and reached the normal range in 12 weeks. These results suggest that elevation of plasma thyroid hormone concentrations in patients with subacute thyroiditis is transient and does not cause any significant change in the RBC Zn concentration.

Induction of experimental thyroiditis in mice by recombinant interferon gamma administration

Expression of major histocompatibility complex (MHC) class 2 molecules on the thyroid follicular cells in human autoimmune thyroid diseases has been reported, and is suggested to play a role in the initiation of the autoimmune responses. Interferon gamma is known to induce MHC class 2 molecules on cultured thyrocytes. Therefore, we administered recombinant interferon gamma to mice to induce MHC class 2 molecule expression in vivo, and investigated the thyroidal changes following MHC class 2 molecule expression. Recombinant interferon gamma 3 x 10(5) U, was administered daily, to mice. MHC class 2 molecules, studied by indirect immunohistochemistry, were expressed on the follicular cells on the 2nd to 4th day after the first interferon gamma administration and continued thereafter. Serum T4 and T3 concentrations decreased and anti-thyroglobulin antibodies and anti-microsomal antibodies were detected. Lymphocyte infiltrations were observed in the thyroid glands obtained at 28 days, but they were mild. These results suggest that MHC class 2 molecule expression on thyroid follicular cells induces anti-thyroid antibodies and plays an important role in the initiation of autoimmune thyroiditis. However, the progression of the immune response to thyroiditis with lymphocyte infiltration may require some other factor. This new model of autoimmune thyroid disease in mice might be useful to elucidate the pathogenesis of human autoimmune thyroid diseases.

Therapeutic potential of two over-the-counter thyroid hormone preparations

Various brands of over-the counter (OTC) exogenous thyroid hormones are available in health food stores and retail pharmacies. Two commercially available OTC thyroid products were analyzed for total thyroxine (T4) and triiodothyronine (T3) content. The strength of a liquid thyroid gland extract was unlabeled and that of the solid oral preparation was 45 mg per table. The T4 concentration of the liquid preparation was less than 10 micrograms/dL; that of T3 was below the analytical sensitivity of our assay (less than 15 ng/dL). Tablet content of T4 and of T3 was up to 0.5 micrograms and up to 50 ng, respectively. Preliminary data on these OTC thyroid gland extracts cannot be extrapolated to all OTC thyroid products, but they suggest that such products generally contain concentrations of T4 and T3 below clinical effectiveness. Further analytical study is warranted.