Continuous infusion of 0.1-10μg/ml of TRH was performed through chronic iv cannulas in unrestrained, unanesthetized hypothyroid rats. Infusion of a constant concentration of TRH induced a peak in the plasma TSH concentration within 5-15min which declined to the baseline within 1h. The refractory period lasted 20-40min after stopping the continuous TRH infusion. A second burst of TSH secretion was induced by increasing the TRH concentration during the refractory period while TRH was being continuously infused. These data indicate that in hypothyroid rats TSH secretion rapidly becomes refractory to continuous exposure to the same concentration of TRH but is stimulated by a higher TRH concentration. This suggests there is heterogeneity in TSH secretory units, which may consist of a constellation of thyrotrophs or of discrete intracellular secretory units, each with a threshold of specific response to TRH.

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To investigate endocrine pathophysiology of luteal phase deficiency (LPD), GnRH/TRH stimulation tests were performed in the early follicular (EFP) and midluteal phases (MLP) of the menstrual cycle in 52 infertile women with a history of short luteal phase, in whom pituitary responsiveness to GnRH/TRH and steroidogenic competency of the corpus luteum were analyzed. Twelve women with either elevated basal-LH or exaggerated PRL response to GnRH/TRH in EFP were eliminated, and the remaining 40 women were studied. Basal-FSH in EFP inversely correlated with steroidogenic parameters in MLP, indicating that compromised folliculogenesis causes LPD. In a fraction of LPD women, decreased basal-LH in MLP was associated with decreased basal-progesterone (p), in spite of normal steroidogenic potential of the corpus luteum, suggesting that aberrant LH secretion is another progenitor of LPD. The other group of LPD women showed shortening of high phase period and/or extravagant discrepancy in endometrial dating without apparent abnormal endocrine parameters, suggesting that unknown factors are involved in establishment of LPD. From the diagnostic point of view, they were discriminated into three groups, normal, incomplete LPD and complete LPD groups, with a modified classification of LPD; 1) shortening of high phase period <11 days, 2) delay in histological to chronological dating of the endometrium >2 days, and 3) decreased max-P in MLP<10ng/ml. Normal (n=14) and complete LPD (n=7) groups consisted of women having all the criteria of classification within and out of the cut-off values, respectively. The remainders were enrolled into incomplete LPD group (n=19). Complete LPD group mainly consisted of women having compromised folliculogenesis as a cause of LPD. In contrast, incomplete LPD group appeared a mixture of heterogenous populations as to the genesis of LPD. GnRH/TSH stimulation test, especially when performed in MLP, would unveil endocrine pathophysiology of LPD and provide an accurate standard for diagnosis of LPD.

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In the present paper we described the first case report of silent thyroiditis following alpha-interferon (IFN-α) treatment for chronic type C hepatitis in Japan. A 51-year-old woman with chronic type C hepatitis was treated with 6 million units of IFN-α three times a week for 24 weeks. Thyroid function was within normal limits and thyroid autoantibodies were negative before IFN therapy. Sixteen weeks after initiation of the treatment, she complained of increasing fatigue, palpitation and losing 7kg in weight. Thyroid function tests at that time revealed an increase in serum T₃, T₄, free T₃ and free T₄ and a markedly suppressed TSH concentration. Both antithyroglobulin antibody (TgAb) and antimicrosomal antibody (McAb) were positive in a dilution of 1:400. The computed tomographic (CT) scan of the thyroid showed a decrease in the CT number (Hounsfield unit; H.U.) to 58 H.U. (normal, 95-167 H.U.). The 24-h thyroid uptake of ¹²³I was 0.75%. Aspiration biopsy specimens from a nodule in the right lobe and the remaining struma disclosed papillary adenocarcinoma and Hashimoto thyroiditis, respectively. Thyroid function spontaneously returned to normal two months after the onset of thyrotoxicosis through the subclinical hypothyroid stage. After recovery of thyroid function, patient had an operation of papillary cancer without any complications. These clinical features and laboratory findings led to the diagnosis of silent thyroiditis developing in the course of the long-term IFN therapy, which, to our knowledge, has not been reported before in Japan.

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The IgG subclass distribution of anti-thyroid peroxidase (TPO) antibodies in patients with chronic thyroiditis and in healthy subjects has been investigated. Anti-TPO antibodies in sera of patients with chronic thyroiditis were predominantly associated with IgG1, with a lesser contribution by IgG4 and IgG3. In contrast, anti-TPO antibodies of healthy subjects were exclusively associated with IgG4. Since structural differences in IgG subclasses reflect differences in their biological roles, these findings suggest that the role of anti-TPO antibodies in patients may differ from that in healthy subjects.

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The aim of this study is to investigate the effect of β-endorphin on cAMP and progesterone accumulation in rat luteal cells. Luteal cells of 4-day-old corpora lutea were cultured for 3h in the absence or presence of 0.001 or 0.01IU/ml hCG, and cAMP, progesterone and β-endorphin levels in the medium were measured by RIA. hCG stimulated the production of cAMP, progesterone and β-endorphin. In the presence of hCG, treatment with islet-activating protein (IAP) led to overall augmentation of cAMP and progesterone accumulation in comparison with untreated controls. In the absence or presence of low doses of hCG (0.001IU/ml), β-endorphin did not affect progesterone production, but inhibited cAMP accumulation. This inhibitory effect was abolished by pre-treatment with TAP. In the presence of high doses of hCG (0.01IU/ml), however, β-endorphin stimulated progesterone production without a corresponding increase in cAMP. This stimulatory effect was also abolished by IAP-treatment. These results suggest that luteal cells produce and release β-endorphin that affects cAMP and progesterone production via IAP-sensitive mechanisms.

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This prospective study was designed to evaluate the potential contributions of high resolution ultrasonography (US) and Tc-99m scintigraphy in the routine diagnosis of thyroid disease. The diagnostic impacts of US and Tc-99m scintigraphy results in 177 patients visiting our thyroid clinic were assessed and scored according to the following criteria: when the information provided by either test supported, confirmed or changed the initial clinical diagnosis, they received scores of 2, 3 and 4 respectively, while score 1 was given when the test itself was useless for the differential diagnosis. US identified focal lesions that both palpation and scintigraphy had failed to detect in 14 (12.1%) of 116 patients with diffuse thyroid diseases, suggesting the necessity of routine US examinations in such patients. US scored higher than scintigraphy in the diagnosis of Hashimoto's thyroiditis, adenoma, adenocarcinoma and adenomatous goiter, and vice versa in the diagnosis of hyperthyroid and euthyroid Graves' diseases. Thus, the advantages of US over scintigraphy for morphological evaluation were confirmed. US was particularly useful for the differential diagnosis of adenomatous goiter from Hashimoto's thyroiditis or a single nodular disease. In contrast, scintigraphy gave functional images, being especially helpful for the differential diagnosis of thyrotoxicosis.

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We examined thyroid hormone autoantibodies (THAA) in 170 patients with untreated Graves' disease (145 women and 25 men, aged 8-74yr). THAA were found in 28 patients (16.5%, group I), but not detected in the remaining 142 patients (83.5%, group II). Neither the male/female ratio nor prevalence of antithyroid antibodies (Ab) (thyroglobulin Ab and/or microsomal Ab) differed between the 2 groups. The mean age of group I was significantly lower than that of group II. Furthermore, prevalence in group I decreased progressively with age. In addition, there was a negative correlation between T₄ Ab titers (but not T₃ Ab titers) and age in group I. These results indicate that the production of THAA, especially T₄ Ab, is influenced by age in untreated Graves' patients. The present study also indicates that the age of the patients is one of the important factors causing different results concerning the prevalence of THAA in Graves' disease.

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To investigate whether thiazolidinediones (AD-4833 and CS-045), new oral antidiabetic agents, are effective in insulin-dependent diabetes mellitus, the effect of thiazolidinediones on streptozotocin-induced diabetic rats was studied by the glucose clamp technique. Diabetic rats were divided into five groups: (1) intensively insulin treated group given a daily injection of 4-6 units Ultralente insulin, (2) AD-4833 group treated with a daily injection of 2 units Ultralente insulin, the minimal dose to make urinary ketones negative, and ingestion of 10mg/kg of AD-4833 suspended in 5% gum arabic, (3) gum arabic group treated in the same way as the AD-4833 group except for the active drug, (4) CS-045 group treated with the same insulin injection and ingestion of 200mg/kg CS-045 suspended in 0.5% chlormethyl cellulose, (5) chlormethyl cellulose group treated as the control for the CS-045 group. Seven days after these treatments, all five groups of diabetic rats and normal control rats were subjected to the glucose clamp study in which 3mU•kg^-1•min^-1 porcine insulin was continuously infused. Glucose infusion rates (GIR) for the gum arabic and chlormethyl cellulose groups were significantly lower than in control rats, and the rates of hepatic glucose output (HGO) of these two groups were not suppressed, indicating the presence of hepatic insulin resistance. Intensive insulin treatment as well as administration of AD-4833 and CS-045 with a minimal dose of insulin restored both GIR and HGO towards normal levels. It is concluded that thiazolidinediones improved hepatic insulin resistance in the presence of a minimal dose of insulin.

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In this study, we determined gene expression of both insulin-like growth factor (IGF)-I and bone Gla protein (BGP; osteocalcin) in calvaria in comparison with their serum levels in methimazole (MMI)-induced congenital hypothyroid (CHT) rats during the first 4 weeks of life. Pups from the MMI-treated dams revealed congenital hypothyroidism with cretinoid physical appearance and showed significant growth retardation compared to the controls. The expression of mRNA for IGF-I in the CHT pups lacked the age-associated increase with a little spurt in their somatic growth rate, although the expression in the controls increased steeply (from 1.86-fold on postnatal day 21 to 3.52-fold on day 28 compared to the day 7 value; P<0.41) according to the spurt in their growth. Moreover, serum IGF-I levels in the CHT rats were significantly lower than those in the controls on postnatal day 28 (63.0±8.0 ng/ml vs. 285.0±33.2ng/ml, respectively; P<0.01). Both BGP gene expression in calvaria and serum intact molecular BGP levels determined by a newly developed ELISA (164.4±15.5ng/ml in the CHT rat vs. 238.6±17.8ng/ml in the control on postnatal day 28; P<0.01) correlated well with the somatic growth in the two groups and clearly demonstrated impaired osteogenesis in the CHT rats. Further studies are needed to clarify how hypothyroidism affects somatic growth and bone metabolism; it is particularly important to understand the autocrine/paracrine mechanisms of action of IGFs in the bone matrix turnover, in vivo.

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A series of chimeric TSH-LH/CG receptors were constructed by substituting homologous segments of the extracellular domain of the rat TSH receptor with corresponding segments of rat LH/CG receptor: C1 (amino acids 37-123 substituted), C2 (91-112), C3 (173-234), C4 (233-266), C5 (268-304), C6 (112-305) and C7 (36-404). After transfection in Cos-7 cell, TSH- and LH/CG- receptor activities of these chimeras were evaluated and compared with those of deletion mutants involving the same residues [Kosugi et al. Thyroid 1:321 (1991)]. Western blot analyses revealed that most of the chimeric receptor proteins were normally synthesized and integrated in the membrane of transfected Cos-7 cells: an antibody to a TSH receptor specific synthetic peptide (residues 352-366) identified 170-190kDa and 90-100kDa TSH receptor structures in the plasma membrane fractions of Cos-7 cells transfected with wild-type TSH receptor cDNA and the C1 to C6 chimeras, but not C7 or wild LH/CG receptor cDNA. Despite this, no receptor except C5 exhibited any significant TSH receptor activities either in [¹²I]TSH binding or in cAMP responses to TSH and thyroid-stimulating antibodies (TSAbs) from Graves' patients. The chimeric receptor C5 exhibited only low affinity TSH binding (Kd=3.5× 10^-8M), as did its counterpart the M2C mutant with residues 268-304 deleted. However, unlike M2C, C5 demonstrated a significant cAMP response to TSH as well as to TSAbs. The cAMP increase in response to TSH in the wild type receptor was observed at 10^-11M TSH. In C5 the response was first evident at 10^-10M TSH, but the maximum cAMP stimulation by TSH and TSAbs in C5 (EC₅₀=6.7× 10^-10M) was approximately the same as the wild type receptor (EC₅₀=1.5×10^-10M). Inhibition of either TSH- or TSAb- stimulated cAMP increase by thyroid-stimulating blocking antibodies (TSBAbs) was also preserved in C5. These results suggest that amino acids 268-304 do not include an important determinant required for signal transduction, since a significant cAMP response to TSH and TSAbs was observed in the C5 receptor with these residues substituted. Additionally, these residues appear to be involved in ligand high affinity binding because high affinity TSH binding was lost in the chimeric receptor C5.

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