Hormonal control in males

1. Hormonal Control of Male
Reproductive Functions
PRESENTED By:
Mashar Rafique
2016-pharmde-034

2. Control of Testes:
• GnRH-secreting neuroendocrine cells fire a brief burst of action
potentials approximately every 2 h, secreting GnRH at these times.
• The GnRH reaching the anterior pituitary via the hypothalamo-
pituitary portal vessels during each periodic pulse triggers the release
of both LH and FSH from the same cell type, not necessarily in equal
amounts.
• systemic plasma concentrations of FSH and LH —rapid increases
during the pulse followed by slow decreases over the next 90 min

4. Action of FSH and LH
• FSH acts only on the Sertoli cells s to stimulate the secretion of
paracrine agents that are essential for spermatogenesis
• whereas LH acts only on the Leydig cells to stimulate testosterone
secretion
• The secretion of FSH is inhibited mainly by inhibin, a protein hormone
secreted by the Sertoli cells,
• and the secretion of LH is inhibited mainly by testosterone, the
hormone secreted by the Leydig cells.
• Testosterone, enters Sertoli cells acting locally, and
facilitates spermatogenesis.

5. Testosterone
• Testosterone inhibits mainly LH secretion.
• It does so in two ways :
• It acts on the hypothalamus to decrease the frequency of GnRH
bursts,
• it acts directly on the anterior pituitary to cause mainly less LH
secretion in response to any given level of GnRH

6. Effects of Testosterone in the Male
1. Required for initiation and maintenance of spermatogenesis (acts via
Sertoli cells)
2. Decreases GnRH secretion via an action on the hypothalamus
3. Inhibits LH secretion via an action on the anterior pituitary
4. Induces differentiation of male accessory reproductive organs and
maintains their function
5. Induces male secondary sex characteristics; opposes action of
estrogen on breast growth

7. Cont.
6. Stimulates protein anabolism, bone growth, and cessation of bone
growth
7. Required for sex drive and may enhance aggressive behavior
8. Stimulates erythropoietin secretion by the kidneys

8. Accessory Reproductive Organs
• The fetal differentiation, and later growth and function of the entire
male duct system, glands, and penis all depend upon testosterone.
• Following castration (removal of the gonads) in the adult male, all the
accessory reproductive organs decrease in size, the glands markedly
reduce their secretion rates, and the smooth-muscle activity of the
ducts is diminished.
• Erection and ejaculation may be deficient. These defects disappear
upon the administration of testosterone.

9. Secondary Sex Characteristics and Growth
• All the male secondary sex characteristics are dependent on
testosterone:
• voice resulting from the growth of the larynx,
• thick secretion of the skin oil glands (this predisposes to acne),
• and the masculine pattern of fat distribution.
• testosterone also stimulates bone growth, largely indirectly through
its stimulation of growth hormone secretion.
• testosterone is an “anabolic steroid” in that it exerts a direct
stimulatory effect on protein synthesis in muscle.

10. Behavior
• Testosterone also plays an important role in maintaining sex drive in
the adult male, although men often remain sexually active, albeit
usually at a reduced level, for years after castration. (This is true only
if the castration occurs during adult life.)
• testosterone-dependent behavioral differences based on gender do
exist in other mammals.