AGE-DEPENDENT CHANGES IN THE PITUITARY-GONADAL RELATIONSHIP: A STUDY OF OVARIAN COMPENSATORY HYPERTROPHY

Abstract

SUMMARY The degree of ovarian compensatory hypertrophy has been studied in unilaterally ovariectomized rats of different ages. Ovarian sensitivity was evaluated by studying the weight increase in response to a standard dose of gonadotrophin (5 i.u. PMS/100 g. body weight/day for 3 days). Little ovarian compensatory hypertrophy was found in immature rats 33 days old. Percentage hypertrophy increased significantly at puberty (day 46) and then levelled out, showing no significant changes (P > 0·05) until the rats weighed over 380 g. and had reached an estimated age of over 9 months when practically no ovarian compensatory hypertrophy was found. No consistent variation in ovarian sensitivity to exogenous PMS attributable to age was found except for an increased response in the prepuberal animals. These results support the view that a significant decline occurs in the output of gonadotrophins from the pituitary gland of the aged rats. The implication of this finding with regard to a decline in reproductive capacity with advancing age is discussed.