These studies indicated that Fsh is involved in the control of puberty and gametogenesis, whereas Lh mainly regulates final gonadal maturation and spawning.
The control of reproductive functions in lower vertebrates has a number of significant differences from that in mammals. Thus, studies of the hormonal regulation of sex gland functions in fish are vital for understanding how these mechanisms develop during reproduction. Gonadotropin could activate the hormone-sensitive adenylate cyclase (AC) via Gs protein leading to formation of cAMP, activation of PKA and CRE, and modulation of gene expression associated with enhanced steroidogenesis.
In vitro experiments on the vitellogenesis of common carp (Cyprinus carpio), tuna (Thunnus thunnus), and chum salmon (Oncorhynchus keta) have shown that Fsh and Lh have equivalent functions in stimulating ovarian steroid production. Sex steroid hormones play important roles at all stages of the reproductive cycle in vertebrates; several studies on their structures and roles in mediating various stages of gonadal development, maturation, and synthesis of Lh in teleost fishes have been reported.