Hypothyroidism in Adult Male Rats Alters Posttranscriptional Mechanisms of Luteinizing Hormone Biosynthesis

Hypothyroidism in Adult Male Rats Alters Posttranscriptional Mechanisms of Luteinizing Hormone Biosynthesis

Autor Romano, Renata Marino Google Scholar
Bargi-Souza, Paula Google Scholar
Brunetto, Erika Lia Google Scholar
Goulart-Silva, Francemilson Google Scholar
Werneck Avellar, Maria Christina Autor UNIFESP Google Scholar
Oliveira, Claudio Alvarenga Google Scholar
Nunes, Maria Tereza Google Scholar
Instituição Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Resumo Background: Studies in men are not consistent regarding the effects of thyroid hormone on the production of gonadotropins. in hypothyroidism consequent to diverse causes, an increase or no change in serum luteinizing hormone (LH) have been reported. the attempt to explain the mechanisms involved in this pathology using rats as an experimental model also seems to repeat this divergence, since hypothyroidism has been shown to induce hypogonadotropic hypogonadism, a hypergonadotropic state, or not to affect the basal levels of LH. Notably, the promoter region of the gene encoding the Lh beta subunit and GnRH (gonadotropin-releasing factor) does not contain a thyroid responsive element. Therefore, we investigated the hypothesis that, in male rats, posttranscriptional mechanisms of LH synthesis are altered in hypothyroidism. We also attempted to determine if hypothyroidism directly affects testicular function in male rats.Methods: Male Wistar rats, 60 days old, were thyroidectomized or sham-operated. After 20 days, they were decapitated, and the pituitaries were collected and analyzed for Lh mRNA, LH content, poly(A) tail length, and polysome profile. the testes were collected and analyzed for Lh receptor mRNA, LH receptor content, and histology using morphometric analyses. the testis, epididymis, seminal vesicle, and ventral prostate were weighed, and serum concentrations of LH, testosterone, thyrotropin (TSH), and triiodothyronine (T3) were measured.Results: Hypothyroidism was associated, in the pituitary, with an increase in Lh mRNA expression, a reduction in Lh mRNA poly(A) tail length, a reduction in the number of LH transcripts associated with polysomes. Pituitary LH was decreased but serum LH was increased from 102 to 543 pg/mL. Despite this, serum testosterone concentrations were decreased from 1.8 to 0.25 ng/mL. A decreased germinative epithelium height of the testes and a reduced weight of androgen-responsive tissues were observed (ventral prostrate: 74 vs. 23 mg/100 g body weight [BW]; seminal vesicle undrained: 280 vs. 70 mg/100 g BW; and seminal vesicle drained: 190 vs. 60mg/100 g BW).Conclusions: Hypothyroidism in adult male rats has dual effects on the pituitary testicular axis. It alters posttranscriptional mechanisms of LH synthesis and probably has a direct effect on testicular function. However, these data suggest the possibility that reduced LH bioactivity may account in part for impaired testicular function.
Idioma Inglês
Financiador Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Número do financiamento FAPESP: 2008/50977-2
FAPESP: 2009/17822-8
CNPq: 305659/2009-0
Data 2013-04-01
Publicado em Thyroid. New Rochelle: Mary Ann Liebert, Inc, v. 23, n. 4, p. 497-505, 2013.
ISSN 1050-7256 (Sherpa/Romeo, fator de impacto)
Editor Mary Ann Liebert, Inc
Extensão 497-505
Fonte http://dx.doi.org/10.1089/thy.2011.0514
Direito de acesso Acesso restrito
Tipo Artigo
Web of Science WOS:000316798700017
URI http://repositorio.unifesp.br/handle/11600/36178

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