Background: What form of estrogen to prescribe a young hypopituitary woman with gonadal failure remains an open question despite evidence that oral estrogen therapy induces growth hormone resistance and an increase in fat mass.

Methods: Using an international surveillance study of hypopituitary patients, we examined two questions: 1) what estrogen is prescribed to young hypopituitary women of fertile years; and 2) is there a difference in body composition or IGF-I levels dependent on type of estrogen prescribed?

Results: 628 growth hormone deficient women aged 18 to 50 yr were identified. 313 had normal gonadal function and 315 were on estrogen therapy, of these 14% were using transdermal estradiol, and 86% an oral estrogen preparation (38% oral estradiol, 18% conjugated estrogens, and 30% ethinyloestradiol in the oral contraceptive). There was no difference in weight, waist/hip ratio, or body composition between the women taking different estrogen therapies. However, if the oral estrogen groups were combined then they showed less change in waist and hip measurement and had a greater waist/hip ratio at one year of growth hormone treatment compared with patients with normal gonadal function (0.85 vs. 0.83; P = 0.022). Patients on ethinyloestradiol had lower age-adjusted IGF-I SD scores (SDS) and required almost twice the growth hormone dose to achieve an IGF-I SDS that remained lower than patients with normal gonadal function and patients on transdermal estradiol.

Conclusions: 1) The majority of hypopituitary women of fertile years take oral estrogen replacement therapy. 2) Waist/hip ratio was greater in women taking oral estrogens; indirect evidence that oral estrogens reduce the action of growth hormone on fat mass. 3) Patients using the oral contraceptive had lower IGF-I levels and required twice the growth hormone dose to patients on transdermal estradiol.