Abolishment of the positive feedback mechanism: A criterion for temporary medical hypophysectomy by LH-RH agonist

The hypothalamic pituitary axis was studied in patients with an abnormal pattern of gonadotropin release during chronic treatment with LH-RH agonist. Two patients had PCOD and the third demonstrated the early luteinization phenomenon. Following a well-defined gonadotropin rise with initiation of LH-RH treatment, no further response was noted. Stabilization of the LH:FSH ratio in PCOD patients was noted after 4 weeks of treatment. Administration of both native LH-RH (100 μg) and intravenous pulsatile LH-RH did not evoke any rise in LH. In addition to the above LH-RH challenges, the positive feedback was examined by administration of estradiol benzoate (EB). The study demonstrated that, although the pituitary did not respond to any LH-RH challenge, it may still respond by a rise in LH following EB administration. Both functions of the hypothalamic pituitary axis should be examined in order to determine the state of medical hypophysectomy.