What controls testosterone and sperm production?
The Physiology of testosterone regulation.
How can the same hormone be necessary for sperm production also cause sperm production to
shut off when extra is given? The pituitary-hypothalamic-gonadal axis is a complex circuit that
controls testosterone and sperm production through two separate feedback loops. The pituitary
gland and hypothalalamus live in the base of the man’s brain and produce the hormones GnRh, LH
and FSH. LH stimulates the Leydig cells of the testis to make testosterone. The testosterone then
gets out of the testis into the blood stream.
When the blood levels of testosterone are normal, the
brain stops secreting LH. When the blood levels of testosterone go down, the brain makes LH to
stimulate the testes to make more testosterone. Testosterone is required in very high concentrations
within the testes for sperm to production to occur. So if a man receives outside testosterone, the
pituitary gland will “think” the testes are making enough testosterone and stop stimulating the Leydig
cells. When the Leydig cells stop making testosterone, the intra-testicular testosterone drops and
sperm production stops.
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