Dose effects of progesterone in add-back therapy during GnRHa treatment

To compare 1 mg norethisterone acetate with 5 mg norethindrone when used in conjunction with 2 mg estradiol given as add-back therapy during treatment with a gonadotropin-releasing hormone agonist (GnRHa).

A prospective, double-blind, randomized study was conducted in a university-based teaching hospital. Forty-seven patients with pelvic endometriosis were recruited. Subcutaneous GnRHa was administered at 6-week intervals, and add-back therapy was commenced with the second dose of GnRHa. Group A patients received 2 mg estradiol and 1 mg norethisterone acetate, while group B patients received 2 mg estradiol and 5 mg norethindrone daily. Changes in bone mineral density, menopausal symptoms, lipid profile and occurrence of breakthrough bleeding were assessed before and after treatment.

Patients in group A had no significant bone loss and satisfactory control of menopausal symptoms. The additional dose of progestogen in group B had a deleterious effect on the lipid profile and increased the frequency of breakthrough bleeding.

In this study, the benefits of add-back therapy during GnRHa treatment were not enhanced, and a deleterious effect upon the lipid profile was seen when using a constant dosage of 2 mg estradiol and 5 mg norethindrone as compared to 1 mg norethisterone acetate.