Thyroid hormone actions on male reproductive system of teleost fish

Author(s)

Tovo-Neto, Aldo ; Rodrigues, Maira da Silva ; Habibi, Hamid R. ; Nobrega, Rafael Henrique

• Document type: Journal article
• Source: General and Comparative Endocrinology; v. 265, p. 7-pg., 2018-09-01.

Abstract

Thyroid hormones (THs) play important roles in the regulation of many biological processes of vertebrates, such as growth, metabolism, morphogenesis and reproduction. An increasing number of studies have been focused on the involvement of THs in the male reproductive system of vertebrates, in particular of fish. Therefore, this mini-review aims to summarize the main findings on THs role in male reproductive system of fish, focusing on sex differentiation, testicular development and spermatogenesis. The existing data in the literature have demonstrated that THs exert their roles at the different levels of the hypothalamic-pituitary-gonadal (HPG) axis. In general a positive correlation has been shown between THs and fish reproductive status; where THs are associated with testicular development, growth and maturation. Recently, the molecular mechanisms underlying the role of THs in spermatogenesis have been unraveled in zebrafish testis. THs promote germ cell proliferation and differentiation by increasing a stimulatory growth factor of spermatogenesis produced by Sertoli cells. In addition, THs enhanced the gonadotropin-induced androgen release in zebrafish testis. Next to their functions in the adult testis, THs are involved in the gonadal sex differentiation through modulating sex-related gene expression, and testicular development via regulation of Sertoli cell proliferation. In conclusion, this mini-review showed that THs modulate the male reproductive system during the different life stages of fish. The physiological and molecular mechanisms showed a link between the thyroid and reproduction, suggesting a possibly co-evolution and interdependence of these two systems. (AU)

• FAPESP's process: 17/09218-0 - Effects of methimazole-induced thyroid hormone insufficiency on zebrafish (Danio rerio) spermatogenesis
• Grantee: Aldo Tovo Neto
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 14/07620-7 - Spermatogonial stem cell bank to preserve the genotype of endangered and valuable teleost species
• Grantee: Rafael Henrique Nóbrega
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 14/16280-5 - Molecular and endocrine control involved on gonadal differentiation of zebrafish (Danio rerio)
• Grantee: Aldo Tovo Neto
• Support Opportunities: Scholarships in Brazil - Doctorate
• 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