Experiments were conducted on young female rats with the aid of morphological, morphometric and histochemical methods; a study was made of the adrenal glands, mammary and the thyroid glands under conditions of castration and administration of synestrol, progesterone, both sex hormones, hydrocortisone. Sex hormones proved to produce a fulminant growth of the glandular tree against the background of reduction of the functional activity of the thyroid gland and relatively high indices of the hormonal activity of the fasciculo-reticular zone of the adrenal glands. A harmonious development of the glandular tree of the mammary glands was noted only under the effect of a simultaneous administration of synesterol and progesteron. A shift in the hormonal balance in the direction of synestrol caused the appearance of pathological deviations in the mammary glands by the type of cystic mastopathy. Under conditions of castration hydrocortisone produced a moderate stimulating influence on the mammary glands only in case of a prolonged action.