Sexual differentiation of the hypothalamus in gonadal agenesis and testicular feminization

Cyclical hypothalamic function was investigated in three patients with an XY karyotype and female external genitalia; in one of them we diagnosed gonadal agenesis, and in the other two testicular feminization. We studied the effect of estradiol and progesterone on gonadotropin release. The patient with gonadal agenesis had cyclical hypothalamic function, but this cyclical function was suppressed in the patients with testicular feminization in whom no LH secretion could be provoked by steroid stimulation. These observations support the concept that hypothalamic sexual differentiation is due to testosterone (which is locally converted to estradiol in the hypothalamus).