Effects of hypothyroidism on the testicular function of Danio rerio and relation between thyroid hormones and hypothalamic-pituitary-testes axis

Author(s)

Maira da Silva Rodrigues

• Document type: Master's Dissertation
• Press: Jaboticabal. 2019-07-31.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2019-07-05
• Advisor: Rafael Henrique Nóbrega

Abstract

Among the hormonal aspects that influence the development of vertebrates, the role of thyroid hormones (Ths) are crucial. These hormones (T4/T3) have a key role on the organism’s homeostasis by modulating physiological processes, including regulation of growth, metabolism and reproduction. This study assessed the effects of in vivo and in vitro hypothyroidism on the testicular function of D. rerio adult males and the interaction between thyroid hormones in the brain-pituitary axis. Here we show that methimazole-induced hypothyroidism in vivo affected the progression of zebrafish spermatogenesis by inducing the accumulation of pre-meiotic cells, delaying cell-differentiation and meiosis as well reducing the number of spermatozoa. It was established in vitro that the effects of the follicle-stimulating hormone (Fsh) on testis function are dependent of thyroid hormones, likewise the stimulatory effects of human chorionic gonadotropin (hCG) and the inhibitory effects of gonadotropin- inhibitory hormone (GnIH) are also subject to Ths. In addition to that, gene expression of brain-pituitary was antagonistically affected both in the absence and in the presence of Ths. These results point to how essential the thyroid hormones are in regulating spermatogenesis and maintaining the brain-pituitary axis in adult zebrafish. Key-words: hypothyroidism, thyroid hormones, spermatogenesis, GnIH, zebrafish (AU)

• FAPESP's process: 17/15793-7 - Effects of hypothyroidism on testicular function of Danio rerio and relation between thyroid hormones and follicle stimulating hormone (Fsh)
• Grantee: Maira da Silva Rodrigues
• Support Opportunities: Scholarships in Brazil - Master