The following points highlight the functions of various types of gonadal hormones.
Gonadal Hormones # Functions of Testosterone:
It is the chief male sex hormone. It is mainly secreted from leydig cells and to some extent from Sertoli cells of testis.
The functions of testosterone are given below:
1. Effects on growth of seminiferous tubule and spermatogenesis:
It helps in growth and maturation of seminiferous tubule. It also stimulates the formation of spermatogonia from primordial germ cells.
2. On sex organs and glands:
It stimulates the growth and functions of epididymis, penis, prostate gland, seminal vesicle. The synthesis of RNA, specific structural and enzymatic proteins is stimulated by this hormone. The prostate and seminal vesicles secrete fructose which acts as nutritive material for the spermatozoa.
3. Effects on secondary male sex characters:
It helps to develop and maintain the secondary sex characters like beards, mustache, masculine voice, distribution of hairs on chest, pubis, back etc. and distribution of pigments on the skin.
4. Anabolic effects:
It increases the synthesis of muscle proteins for well-built musculature. It also increases the Ca++ deposition in bones.
5. On blood:
It increases haemoglobin content in blood.
6. On metabolism:
It increases BMR.
7. On skin:
It increases the thickness of skin and also increases secretion of sebum from sebaceous gland.
8. On behaviour:
It produces aggressive behaviour and interest in the opposite sex.
Gonadal Hormones # Functions of Estrogen:
Estrogen a female sex hormone (for structure and biosynthesis of estrogen see chapter 6). Now a day’s synthetic estrogens are used in clinical therapy.
Functions of estrogen are given below:
1. On ovary:
It has a direct stimulatory effect on the follicular growth.
2. On female sex characters:
It helps to stimulate the growth of breast, uterus and vagina at puberty. It changes the vaginal epithelium. The external genitalia become enlarged by the effect of estrogen with the deposition of fat.
3. On secondary female sex characters:
It helps in deposition of subcutaneous fat, specially in breast and buttocks. It leads to the development of feminine voice, narrow shoulder and broad hips.
4. On mammary glands:
It primarily stimulates the growth of an extensive ductile system of mammary gland.
5. Anabolic effect:
It promotes retention of sodium, calcium and phosphates in the body. It causes uptake of Ca++ from bones.
6. On reproductive cycle:
The physiologic levels of estrogen promote the pituitary release of LH for ovulation.
Gonadal Hormones # Functions of Progesterone:
Progesterone is one of the main female sex hormone. It is chiefly secreted from corpus luteum.
The functions of progesterone are given below:
1. On uterus:
It promotes secretory changes in the endometrium of the uterus and prepares the uterus for implantation of fertilized ovum.
2. On placenta:
During pregnancy, it helps to maintain the placenta, as well as gestation.
3. On mammary gland:
It helps in the proliferation of alveolobular system of mammary gland for secretion.
4. On ovarian follicles:
This hormone inhibits follicular maturation during pregnancy.
5. On body temperature:
It is thermo-genic and is usually responsible for the rise in basal temperature at the time of ovulation.
Gonadal Hormones # Functions of Gastrointestinal Hormones:
Gastrointestinal tract plays many roles by secreting various peptide hormones. The gut hormones are localized to specific cells distributed throughout the Gl tract. A number of Gl hormones have proven useful in clinical practice. Physiological roles of the Gl hormones are given below tabular form (Table 5.3).
