Review article

Biochemical mechanisms of sex hormones synthesis in domestic mammals

Erika Gamulin ; Hrvatska
Marko Samardžija orcid.org/0000-0003-0402-3173 ; Veterinarski fakultet Sveučilišta u Zagrebu, Hrvatska
Ivan Butković ; Veterinarski fakultet Sveučilišta u Zagrebu, Hrvatska
Jelka Pleadin ; Hrvatski veterinarski institut, Zagreb, Hrvatska

Abstract

Sex hormones are steroids synthesized by the gonads through multiple biochemical mechanisms. In mammalian systems, there are six groups of steroid hormones that can be classified on both a structural and a biological (hormonal) basis. They are the oestrogens and progestins (female sex steroids), androgens (male sex hormones), mineralocorticoids (al- dosterone), glucocorticoids (cortisol) and vita- min D. They are all derived from cholesterol. The parent ring structure for cholesterol is the fully saturated ring structure cholestane. Ste- roid hormones are fat-soluble, enabling their entry into all body cells as lipid cellular barri- ers are not a barrier for them. Regulatory cog- nitive production of sex hormones is a com- plex process, and all mechanisms take place through the hypothalamus-pituitary-ovarian linkages. Hormone biosynthesis determines the sex cycle of the animals, but also depends on the sex cycle of the same individuals, there- fore biosynthesis in pregnancy is different from that in reproductive age. Pregnancy is characterized by a massive increase in the pro-
duction of both progesterone and oestrogen. The increase in progesterone and oestradiol production occurs only in the placenta. Male sex hormones (androgens) are steroids with 19 C-atoms, while female hormones are steroids with 18 C-atoms (oestrogens) and 21 C-atoms (progesterone). Androgens are synthesized in the Leydig’s cells, progesterone in the cor- pus luteum, and oestrogen in the ovaries and corpus luteum, while lesser amounts are pro- duced in the testicles and the adrenal gland. In the mitochondria, cholesterol is converted into pregnenolone, the precursor steroid required for synthesis of all the steroid hormones. The reactions are catalysed by enzymes such as: P450scc, StAR, 5α-reductase. The most active oestrogen is 17β-oestradiol, and testosterone 5α-dihydrotestosterone (5α-DHT). Progester- one, testosterone and oestradiol have multiple roles in sex cycles, and their function depends on the physiological synthesis of the hor- mones themselves.

Keywords

sex hormones; androgens; oestrogens; progesterone; biochemistry

Hrčak ID:

223214

URI

https://hrcak.srce.hr/223214

Publication date:

8.12.2018.

Article data in other languages: croatian

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