Introduction Thyrotropin (thyroid-stimulating hormone, TSH) is a heterodimer consisting of the TSH-specific β subunit (TSHβ) and the chorionic gonadotropin α chain (CGA) that is common to luteinizing hormone (LH), follicle-stimulating hormone (FSH
Koji Nagayama, Shigekazu Sasaki, Akio Matsushita, Kenji Ohba, Hiroyuki Iwaki, Hideyuki Matsunaga, Shingo Suzuki, Hiroko Misawa, Keiko Ishizuka, Yutaka Oki, Jaeduk Yoshimura Noh, and Hirotoshi Nakamura
C. A. Ollis, D. S. Munro, and S. Tomlinson
We have described a system for the maintenance in culture of isolated human thyroid cells from both thyrotoxic tissue and non-toxic goitres. The cells isolated from the two thyroid tissue types showed similar cyclic AMP response characteristics to TSH with large increases in intracellular and extracellular cyclic AMP after 20-min incubations. Maximal responses were obtained with 50 mu. TSH/ml and half-maximal responses at 1·0 mu. TSH/ml. With cell passage the cyclic AMP responses to TSH decreased in magnitude and sensitivity. As with other thyroid cultures, growth of the cells with TSH induced arrangement into follicular structures, whereas cells grown in the absence of TSH remained as a monolayer. Basal intracellular cyclic AMP levels were increased in a dose-related fashion in cells grown in the presence of graded concentrations of TSH and the maximal response to further additions of TSH was not greater than in control cultures.
M Theodoropoulou, T Arzberger, Y Gruebler, Z Korali, P Mortini, W Joba, AE Heufelder, GK Stalla, and L Schaaf
Thyrotrophin (TSH) synthesis and secretion is under the positive control of thyrotrophin releasing hormone and under the negative control of the thyroid hormones. However, it is hypothesised that TSH has a direct effect on the regulation of its own synthesis through an intrapituitary loop mediated by pituitary TSH receptors (TSH-R). The aim of this investigation was to study the expression of TSH-R in normal human pituitary at mRNA and protein levels, and to compare the pattern of protein expression between different pituitary adenomas. Using RT-PCR we were able to detect TSH-R mRNA in the normal pituitary, and immunohistochemical studies showed TSH-R protein expression in distinct areas of the anterior pituitary. Double immunostaining with antibodies against each of the intrapituitary hormones and S100 revealed that TSH-R protein is present in thyrotrophs and folliculostellate cells. Examination of 58 pituitary adenomas, including two clinically active and two clinically inactive thyrotroph adenomas, revealed TSH-R immunopositivity in only the two clinically inactive thyrotroph adenomas. This study shows, for the first time, the presence of TSH-R protein in the normal anterior pituitary and in a subset of thyrotroph adenomas. The expression of TSH-R in the thyrotroph and folliculostellate cell subpopulations provides preliminary evidence of a role for TSH in autocrine and paracrine regulatory pathways within the anterior pituitary gland.
P. J. D. DAWES, V. B. PETERSEN, B. REES SMITH, and R. HALL
Thyrotrophin (TSH) receptors have been extracted from human and porcine thyroid membranes by treatment with Triton X-100.125I-Labelled bovine TSH was used to monitor receptor activity. Analysis by gel filtration and electrophoresis on acrylamide gels containing sodium dodecyl sulphate suggested that Triton extracts of human thyroid membranes contained TSH receptors with a molecular weight in the region of 50 000 closely associated with Triton micelles of approximate molecular weight 300 000. Isoelectric focusing studies indicated that the Triton-solubilized TSH binding activity had an isoelectric point of pH 4–4·5. The soluble TSH receptors were heat-labile, showed optimum TSH binding at pH 7·4 and reduced hormone binding at high ionic strength. The TSH binding characteristics of membrane-bound and solubilized human TSH receptors were similar and both preparations gave curved Scatchard plots.
Solubilized porcine TSH receptors appeared to have a similar molecular weight to the human receptors and were also closely associated with Triton micelles of approximate molecular weight 300 000. Scatchard analysis of TSH binding to membrane-bound or solubilized porcine TSH receptors gave approximately linear plots with association constants of 2·8 ± 0·95 (s.e.m.) × 109 and 1·7 ± 0·27 × 1091/mol respectively. Comparison of the binding capacities of the solubilized and membrane-bound porcine receptors indicated that the 0·5% Triton extracts contained 40% of the original TSH binding activity and that this was present at a concentration of 25 ng/ml.
Ling Jin, Vanessa Chico-Galdo, Claude Massart, Christine Gervy, Viviane De Maertelaere, Marvin Friedman, and Jacqueline Van Sande
variation (CV) is less than 3.4% for values between 2 and 13 pg/ml and for FT 4 the CV is less than 3.5% for values between 0.7 and 4 ng/dl. Thyrotropin (TSH) was evaluated by bioassay using a line of Chinese hamster ovary cells (CHO-K1) stably transfected
Norbert Chauvet, Taoufik El-Yandouzi, Marie-Noëlle Mathieu, Audrey Schlernitzauer, Evelyne Galibert, Chrystel Lafont, Paul Le Tissier, Iain C Robinson, Patrice Mollard, and Nathalie Coutry
examined β-catenin distribution by immunohistochemistry on sections from adult pituitary gland double-stained with antibodies against β-catenin and the different hormones produced by the gland (GH, TSH, FSH, LH, ACTH, and PRL). Overall, β-catenin was
J. A. Franklyn, D. F. Wood, N. J. Balfour, D. B. Ramsden, K. Docherty, and M. C. Sheppard
The role of oestrogen in the regulation of TSH gene expression is unclear. We have examined the effect of administration of oestrogen in the rat on serum TSH, pituitary TSH content and pituitary cytoplasmic concentrations of mRNA encoding the TSH β and α subunits, thus deriving measures of hormone release and synthesis. In addition, we have examined the effect of oestrogen on the binding of tri-iodothyronine (T3) to nuclear receptors in the anterior pituitary.
Administration of oestrogen did not affect serum concentrations of TSH in euthyroid or untreated hypothyroid rats, but did augment the effects of T3 (1 and 2 μg on serum TSH in hypothyroid animals 6 h after injection of T3. No influence of oestrogen or of thyroid status on pituitary content of TSH was seen.
A marked increase in the concentrations of TSH β and α mRNA in pituitary cytoplasm was found in hypothyroidism, compared with those in the euthyroid state. No effect of oestrogen on TSH mRNA was seen in euthyroid animals but concentrations of TSH β and α mRNA were lower in hypothyroid animals than in vehicle-treated controls. A stimulatory influence of T3 on TSH mRNA was seen 6 h after injection of T3; this stimulation was absent in oestrogen-treated rats. No effect of oestrogen on the action of T3 was evident 72 h after beginning treatment with T3. In addition to effects on serum TSH and TSH mRNA, an increase in the number of pituitary nuclear receptors for T3 was seen after oestrogen treatment.
The influences of oestrogen on serum TSH and on TSH mRNA are consistent with augmentation of thyroid hormone effects; this influence may be mediated by an increase in the number of pituitary nuclear receptors for T3.
J. Endocr. (1987) 115, 53–59
Sharon E Mitchell, Ruben Nogueiras, Kellie Rance, D Vernon Rayner, Sharon Wood, Carlos Dieguez, and Lynda M Williams
). Thyroid-stimulating hormone (TSH) was measured by RIA as previously described ( Seoane et al. 2000 ) using reagents provided by the National Hormone and Peptide Program (NHPP; Torrance, CA, USA). Sequencing of the GHS-R promoter
S. W. MANLEY, J. R. BOURKE, and R. W. HAWKER
Immunoglobulin G (IgG) prepared from sera containing the long-acting thyroid stimulator (LATS) inhibited the receptor binding of 125I-labelled thyrotrophin (TSH) in a particulate fraction of guinea-pig thyroid homogenate. This inhibition was shown to involve a binding interaction between IgG containing LATS and the receptor with a diminution in the number, but not affinity, of sites available for binding of TSH. Studies of dissociation kinetics and gel filtration of receptor—TSH complexes indicated that IgG containing LATS did not combine with receptors occupied by TSH. The data provide evidence that LATS and TSH bind to the same receptor site.
JILL BROWN and D. S. MUNRO
A new in vitro assay for thyroid-stimulating hormone (TSH) is described. The parameter of TSH action is the discharge of radioactive iodine from mouse thyroid glands labelled with 131I in vivo. The assay is sensitive to human TSH and gave consistent results during 1 yr. without seasonal variation. A potent preparation of long-acting thyroid stimulator gave a dose-response line parallel with human TSH. Fresh human serum was toxic to the assay preparation so that circulating TSH levels cannot be measured.