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SUMMARY
Thyrotrophin (TSH) release in response to intravenous synthetic thyrotrophin releasing hormone (TRH) was unaltered by simultaneous corticotrophin (ACTH) and growth hormone secretion induced by hypoglycaemia or methylamphetamine in normal subjects. Secretion of growth hormone was the same whether or not TSH was secreted. While the increments in plasma corticosteroids and ACTH after methylamphetamine administration were not different whether TRH or a control injection was given, they rose more during insulin-induced hypoglycaemia when TRH was given as well. This could have been due to a slightly greater degree of stress after TRH + insulin than insulin alone. Overnight dexamethasone suppression of basal ACTH secretion did not alter the TSH response to TRH. Unlike the rat, there is no evidence suggesting competition between pituitary mechanisms involved in ACTH, growth hormone and TSH release in man.
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Thyroid-stimulating hormone (TSH) has been shown to increase the radioactive iodine uptake and the blood flow in the thyroid gland (Söderberg, 1958; Solomon, Prujan & Triplett, 1963; Clayton & Szego, 1967) but there are also negative reports of its effects on the thyroid circulation (Isaacs & Rosenberg, 1967). An attempt has been made to contribute to this problem by examining some effects of TSH on thyroid 86Rb and 131I uptake in rats.
Young female rats weighing 60–100 g. (the difference of weights not exceeding 20 g. in individual experiments), fed standard laboratory diet (Larsen) and water ad libitum, were used. Endogenous TSH secretion was inhibited by adding 0·1% desiccated thyroid (Thyreoidin Spofa) to the food for 7 days. TSH (Thyreotropin Spofa, batch A021066) was injected into the tail vein in doses from 0·1 to 1000·0 m-u. in 0·2 ml. saline. Thyroid 86Rb uptake was measured 40 sec.
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SUMMARY
Antisera were produced in rabbits against highly purified preparations of human LH (2000 or 10000 i.u./mg), human FSH (5500 i.u./mg), and human TSH (7·5 i.u./mg). Most rabbits produced antisera of high titre and high avidity. Cross-reactions were minimal between human TSH and human chorionic gonadotrophin (HCG) and between human FSH and HCG but marked between human LH and HCG. TSH and FSH also showed a constant but relatively weak cross-reaction. LH cross-reacted with FSH to a higher degree than did HCG. The avidity of the antisera was high. It was concluded that much of the lack of specificity recorded for glycoprotein antisera are effects of impure immunogens. Some of the true cross-reactions are probably explained by shared antigenic determinants of the β-subunits. Unadsorbed antisera could be used for assay of FSH and TSH in plasma from pregnant women.
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SUMMARY
The urinary excretion of thyroid-stimulating hormone (TSH) has been measured by double antibody radioimmunoassay after concentration by dialysis followed by lyophilization. Among 30 normal subjects, the excretion was 5·6 ± 0·31 (s.e.m.) μu./h. No diurnal variation nor differences between sexes were discerned. In 14 primary hypothyroid subjects the urinary excretion was raised (P < 0·001) to 25·1 ± 3·3 μu./h. In 14 hyperthyroid and 7 hypopituitary subjects subnormal levels of 2·6 ± 0·2 and 2·5 ± 0·22 μu./h (P < 0·001) respectively, were found. Serum and urinary TSH concentrations were measured before, during and after an infusion of human pituitary TSH (MRC 70/9) in two subjects and showed a correlation.
Urinary TSH measurement is thus a good discriminant between normal and hyperthyroid or hypopituitary patients.
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Oestrogens probably influence thyroid function through several mechanisms (Brown-Grant, 1960; Ślebodziński, 1962; Plunkett, Squires & Heagy, 1963) and whether the effect is stimulant or depressant depends on dosage, duration of treatment and probably on species.
Two types of hypothalamic lesions have been described which interfere with TSH release in the rat. Relatively small lesions in the anterior hypothalamus and the suprachiasmatic region are claimed to block the release of TSH with enhanced demand, e.g. during exposure to cold (D'Angelo, 1960) or administration of goitrogens (Bogdanove & Halmi, 1953). The importance of this area for TSH release has been questioned (e.g. van Beugen & van der Werff ten Bosch, 1960). However, there is general agreement that more posterior lesions of the median eminence block TSH release under all conditions (Harris, 1960), although this effect may be due to pituitary infarction.
The effect of electrolytic lesions in these two positions on 131
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SUMMARY
Attempts to isolate, free of thyroid-stimulating hormone (TSH), the peptide(s) responsible for the lipolytic activity of a fraction of acetone-dried human pituitary powder are described. It was not found possible to separate the lipolytic and TSH activities, even by isoelectric focusing which gave fractions consisting predominantly of single protein components. In the four lipolytic fractions isolated by electrofocusing, the two activities paralleled one another. It is therefore concluded that the TSH present is responsible for the lipolytic activity of this human pituitary fraction, though some evidence suggests that luteinizing hormone (LH), which is a minor contaminant, might also be lipolytic.
The minimum effective lipolytic concentration of the most potent fraction isolated was in the range 0·1–1·0 μg/ml. This is far in excess of plasma concentrations of TSH or LH encountered physiologically. Hence the lipolytic action of these molecules is unlikely to be of physiological significance.
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SUMMARY
125I-Labelled thyrotrophin (TSH) showed saturable binding to hyperplastic guinea-pig thyroid slices in vitro, but not to kidney, adrenal, liver, testis or salivary gland slices. Two populations of binding sites were demonstrated: high order sites showed an affinity constant of 3·8 × 1081/mol and a capacity of 8 × 103 molecules of TSH/cell; low order sites, affinity constant of 2·9 × 1071/mol and capacity of 8 × 104 molecules/cell. The highorder sites saturate at about 1 mu./ml, approximately the level producing maximal in-vivo and in-vitro responses. Binding of 125I-labelled TSH was reversible, the released hormone appearing substantially unchanged as assessed by chromatographic behaviour and antiserum binding. Release of unlabelled TSH from pre-incubated thyroid slices was demonstrated by bioassay. Bovine thyroid slices were found to have a lower capacity for binding than hyperplastic guinea-pig slices.
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Thyrotropin (TSH) and transforming growth factor beta 1 (TGFbeta1) have major roles in the regulation of folliculogenesis and differentiation in thyroid cells. Isolated porcine thyroid cells cultured in the presence of TSH on a plastic surface recover a follicular architecture and exhibit normal functional properties. The addition of TGFbeta1 to the culture medium induces important morphological changes and extracellular matrix remodelling. Similarly, thyroid cells lose their ability to organify iodine and their responsiveness to adenylate cyclase. The aim of this study was to analyse the influence of TGFbeta1 on the functional activity of thyrocytes in suspension culture, independent of follicle disruption. In this system, we demonstrate that TGFbeta1 inhibits expression of thyroperoxidase, NADPH oxidase activity, iodine uptake and, consequently, iodine organification. Moreover, TGFbeta1 decreases basal and TSH-stimulated cAMP production and TSH receptor expression. Taken together, these data converge to demonstrate an essential role of TGFbeta1 in the regulation of the thyroid cell function.
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A protein which shared several characteristics with authentic calmodulin was extracted from human thyroid homogenates. The protein bound to fluphenazine–Sepharose and could be specifically eluted using EGTA. The eluted protein had a u.v. spectrum characteristic of calmodulin and migrated like authentic calmodulin with a calcium-dependent shift on sodium dodecyl sulphate polyacrylamide-gel electrophoresis. Calmodulin in thyroid cell extracts was shown to be biologically active, measured by its ability to activate a calmodulin-deficient cyclic GMP phosphodiesterase; this activation could be inhibited by trifluoperazine. A possible role for calmodulin in the action of TSH on the thyroid was demonstrated by studying the effects of phenothiazines and the naphthalene sulphonamide, W7, a more specific calmodulin inhibitor, on TSH-stimulated cyclic AMP levels in cultured thyroid cells. The phenothiazines and W7 were found to inhibit the accumulation of cyclic AMP in response to TSH in a concentration-dependent manner although low concentrations of W7 enhanced TSH-stimulated cyclic AMP accumulation.
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ABSTRACT
Thyrotrophin in individual pituitaries obtained from fetal and prepubertal pigs was quantified by homologous radioimmunoassay (RIA) and heterologous radioreceptor assay (RRA). Relative evolution of pituitary TSH contents and concentrations with age were in good agreement as measured by both assay systems although the quantity of TSH detected by RRA appeared consistently lower than that measured by RIA. Thyrotrophin was first detected in pituitaries of fetal pigs at day 75 of gestation. Thereafter the pituitary content of TSH increased to approximately 45 μg/pituitary in the oldest group tested (6 weeks of age). The pituitary TSH concentration rose sharply until birth (114±1 day post coitum) and thereafter remained increased at a concentration of approximately 400 ng/mg wet weight.
J. Endocr. (1986) 111, 111–115