The androgens and oestrogens represent the major male and female sex hormones respectively.
The testicular Leydig cells represent the primary source of androgens in the male, of which testosterone is the major one. Testosterone, in turn, serves as a precursor for two additional steroids, i.e. dihydrotestosterone and the oestrogen called oestradiol. These mediate many of its biological effects.
Females, too, produce androgens, principally in the follicular theca cells. Androgens are also produced in the adrenals in both male and females.
The biological activities of androgens (only some of which are specific to males) may be summarized as:
1. promoting and regulating development of the male
phenotype during embryonic development.
2. promoting sperm cell synthesis.
3. promoting development and maintenance of male
secondary sexual characteristics at/after puberty.
4. general growth-promoting effects.
5. behavioural effects (e.g. male aggressiveness, etc).
6. regulation of serum gonadotrophin levels.
The follicular granulosa cells are the major site of synthesis of female steroid sex hormones: the oestrogens. β-Oestradiol represents the principal female follicular oestrogen. Oestriol is produced by the placenta of pregnant females. Oestriol and oestrone are also produced in small quantities as products of β-oestradiol metabolism.
Testosterone represents the immediate precursor of the oestrogens, the conversion being catalysed by the aromatase complex, i.e. a microsomal enzyme system. The biological actions of oestrogens may be summarized as:
1. growth and maturation of the female reproductive system.
2. maintenance of reproductive capacity.
3. development and maintenance of female secondary sexual
characteristics.
4. female behavioural effects.
5. complex effects upon lipid metabolism and distribution of
body fat.
6. regulation of bone metabolism (oestrogen deficiency
promotes bone decalcification, as seen in postmenopausal
osteoporosis).
The testicular Leydig cells represent the primary source of androgens in the male, of which testosterone is the major one. Testosterone, in turn, serves as a precursor for two additional steroids, i.e. dihydrotestosterone and the oestrogen called oestradiol. These mediate many of its biological effects.
Females, too, produce androgens, principally in the follicular theca cells. Androgens are also produced in the adrenals in both male and females.
The biological activities of androgens (only some of which are specific to males) may be summarized as:
1. promoting and regulating development of the male
phenotype during embryonic development.
2. promoting sperm cell synthesis.
3. promoting development and maintenance of male
secondary sexual characteristics at/after puberty.
4. general growth-promoting effects.
5. behavioural effects (e.g. male aggressiveness, etc).
6. regulation of serum gonadotrophin levels.
The follicular granulosa cells are the major site of synthesis of female steroid sex hormones: the oestrogens. β-Oestradiol represents the principal female follicular oestrogen. Oestriol is produced by the placenta of pregnant females. Oestriol and oestrone are also produced in small quantities as products of β-oestradiol metabolism.
Testosterone represents the immediate precursor of the oestrogens, the conversion being catalysed by the aromatase complex, i.e. a microsomal enzyme system. The biological actions of oestrogens may be summarized as:
1. growth and maturation of the female reproductive system.
2. maintenance of reproductive capacity.
3. development and maintenance of female secondary sexual
characteristics.
4. female behavioural effects.
5. complex effects upon lipid metabolism and distribution of
body fat.
6. regulation of bone metabolism (oestrogen deficiency
promotes bone decalcification, as seen in postmenopausal
osteoporosis).
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