Response of plasma LH and FSH to gonadotropin-releasing hormone in pony foals and ovariectomized pony mares.

ABSTRACT

Plasma FSH and LH response to a synthetic GnRH analog was measured in adult ovariectomized pony mares (OVX) and in pony foals (<70 days of age) during late spring (May-June). FSH and LH responded in a similar fashion (200% increase) in the OVX mare, which is different from other reports for intact mares. There was a greater mean response to a comparable dose of GnRH in the prepubertal foal for both FSH (500%) and LH (900%) than in the OVX mare. There was a positive correlation between age and the maximum FSH response to GnRH in male and female foals. The LH response was positively correlated with age in male foals, but not in females. The response to GnRH in the prepubertal foals was consistent with the previously observed patterns of gonadotropin secretion during this age period.