1. Reproduction Physiology
Irfan Idris
Physiology Department, Medical Faculty, UNHAS

4. Modified from R. Guillemin & R. Burgus (1972)‏
The hormones of the hypothalamus, Sci Am 227:24-33.
Modified from R. Guillemin & R. Burgus (1972)‏
The hormones of the hypothalamus, Sci Am 227:24-33.

6. © Kenneth L. Campbell, 1997. All rights reserved.

7. © Kenneth L. Campbell, 1997. All rights reserved.

10. Puberty the onset of puberty has long been a mystery
during childhood the hypothalamus simply does not secrete significant amounts of GnRH/LHRH
the slightest secretion of any sex steroid hormones exerts a strong inhibitory effect on hypothalamic secretion of GnRH/LHRH
at the time of puberty, the secretion of hypothalamic GnRH breaks through the childhood inhibition, and adult sexual life begins

11. Experimental evidence suggests that this rise in gonadotropin secretion is a result of two processes:
maturational changes in the brain that result in increased GnRH secretion by the hypothalamus
decreased sensitivity of gonadotropin secretion to the negative feedback effects of sex steroid hormones
the sensitivity of the hypothalamus and the pituitary to negative feedback effects decreases at puberty, which would also help to account for rising gonadotropin secretion at this time

35. The Sertoli cells of the seminiferous tubules secrete müllerian inhibition factor (MIF), a polypeptide that causes regression of the müllerian ducts beginning at about day 60.
The secretion of testosterone by the Leydig cells of the testes subsequently causes growth and development of the wolffian ducts into male accessory sex organs
Testosterone is converted by the enzyme 5α-reductase into the active hormone known as dihydrotestosterone (DHT).
DHT is needed for the development and maintenance of the penis, spongy urethra, scrotum, and prostate. Evidence suggests that testosterone itself directly stimulates the wolffian duct derivatives—epididymis, ductus deferens, ejaculatory duct, and seminal vesicles