Thyroid hormone actions on male reproductive system of teleost fish

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.

Seasonal Related Multifactorial Control of Pituitary Gonadotropin and Growth Hormone in Female Goldfish: Influences of Neuropeptides and Thyroid Hormone

“…In isolated rainbow trout ovarian follicles, T3 treatments enhanced gonadotropin-induced E2 secretion (53). In male fish, thyroid hormones significantly alter spermatogenesis (56). In zebrafish, T3 treatment was shown to stimulate Sertoli cell and spermatogonia type-A proliferation in testis (62).…”

“…A number of studies have demonstrated actions of thyroid hormone on reproduction in both female and male (52)(53)(54)(55)(56). In murrel, Channa gachua, and a carp, Catla catla, as well as Ranid frogs, GnRH variants increased plasma T4 levels (57,58), although no changes in T3 levels were observed in the goldfish following GnRH treatment (59).…”

De novo transcriptome assembly of four organs of Collichthys lucidus and identification of genes involved in sex determination and reproduction

“…A total of 27,708 unigenes were clustered into 67 GO terms under three different GO categories containing (biological process (BP), cellular component (CC) and molecular function (MF). The number of unigenes in each GO term were shown in Fig 2A. The top 3 terms ranked by number of unigenes in BP were cellular process (17,477), single-organismal process (16,219) and biological regulation (11,558). For CC, unigenes were mainly involved in cell (16,229), cell part (16,151) and membrane (11,815).…”

“…The number of unigenes in each GO term were shown in Fig 2A. The top 3 terms ranked by number of unigenes in BP were cellular process (17,477), single-organismal process (16,219) and biological regulation (11,558). For CC, unigenes were mainly involved in cell (16,229), cell part (16,151) and membrane (11,815). For MF, binding (16,123) was the most prevalent, followed by nucleic acid binding catalytic activity (10,504) and signal transducer activity (1,974).…”

“…Abnormal HPG axis can lead to defective reproductive performance of animals. As previous article reported, a variety of natural or synthetic compounds, such as monocrotophos pesticide, semicarbazide and thyroid hormones, could lead to significant effect on fish reproduction through HPG [11][12][13]. For example, Hou et al investigated the effects of norethindrone on gonad differentiation and sex determination of juvenile zebrafish Dario renio, and revealed that the expressions of genes associated with the HPG axis was altered by exposure to norethindrone, thus resulting in affecting sex differentiation [14].…”