The interaction of steroids with the hypothalamic-pituitary-testicular system in the adult male rat

Major functions of the mature male gonad are the production of gametes and steroid hormones. Extratesticular as well as intratesticular factors regulate these two male gonadal functions which are associated with two distinct cell compartments in the testis. It has been known for a long time that hypophysectomy is followed by gonadal atrophy and arrest of the spermatogenic process which only will proceed to a primary spermatocyte stage. The anterior pituitary gland appears to play an essential role in the regulation of the testis and systematic studies on the relationship between brain structures and the male gonad started in the late nineteen twenties and early thirties. The finding that testicular functions were controlled by the hypophysis stimulated almost simultaneously experiments on the reverse issue, i.e. whether testicular products can affect the hypophysis (Moore and Price, 1930). The connections between these systems are the anterior pituitary gonadotrophiC hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It is now well established that the major control of pituitary function resides in the hypothalamus, although other brain structures also are involved in the regulation of the pituitary gland (Szent.3.gothai et al. 1968; Mess and Martini, 1968; Halasz, 1969). Hypothalamic gonadotrophin releasing factor (GnRF) , reaching the anterior pituitary gland via a portal system, stimulates syn-thesis (Redding et al. 1972) and release (Schally et al. 1968) of the hypophyseal gonadotrophins LH and FSH in special gonadotroph cells. The many mutually dependent and complicated interactions between hypothalamus, hypophysis and testis at different functional levels are intriguing and make their study very attractive.