SUN-044 Gonadotropin Releasing Hormone (GnRH) Agonist Therapy Induces a Sustained Reduction in Plasma Testosterone Levels and Is Well Tolerated in Transwomen Veterans

Gender affirming hormone therapy (GAHT) is the mainstay of long-term management of transgender individuals. In transwomen, treatment with physiologic doses of estrogen alone is often insufficient to suppress testosterone to the desired level. Although GnRH agonist therapy is usually prescribed for puberty suppression in trans youth, in adult transwomen, GnRH agonist may be added. The durability of long-term GnRH agonist in lowering testosterone as well as the long-term safety is not clear. We examined the effect of leuprolide a GnRH agonist, on testosterone as well as clinical and metabolic features in transwomen Veterans. Out of 91 subjects with gender dysphoria followed at a VA Endocrinology clinic, 65 were transwomen (age 49 ± 3 years) who had a detailed clinical, biochemical and hormonal profile (lipid profile, HbA(1C), FPG, testosterone, estradiol). We performed a retrospective cohort study of the 31 (48%) transwomen on Leuprolide (3.375mg q month) and 33 transwomen who were not on Leuprolide. Plasma testosterone, lipid profile, were analyzed before, 6 months, 1 year and at the last follow-up visit. The median follow-up of subjects on Leuprolide was 2.7 (1.7-3.8) years. Plasma testosterone concentration declined by 89% from 432±32 ng/dl to 47±9 ng/dl within 3-6 months after initiation of GnRH agonist treatment. Plasma testosterone remained persistently low 39±4ng/dl at 1 year and at the end of 2.7 yrs, most subjects on Leurprolide had plasma testosterone concentration <50ng/dl. Leuprolide therapy led to similar rapid decline in testosterone concentration in both younger (<40yrs) or relatively older (>50yr) transwomen. Leuprolide was in general well tolerated requiring discontinuation in just one patient due to severe fatigue. Three subjects (10%) experienced hot flashes which did not lead to discontinuation of medication. In the non-Leuprolide group, of 33 subjects, the follow-up was relatively inconsistent and only 12 subjects were regularly followed throughout a year with stable treatment. The decline in plasma testosterone was of a lower magnitude versus the leuprolide group (55% vs 89%, p <0.05). The testosterone levels declined from 393±42 to 180±44 ng/dl at 6 months. Body weight, and lipid profile: triglyceride, and plasma HDL concentration did not change significantly with or without GnRH agonist therapy. In conclusion, GnRH agonist therapy led to a sustained suppression of plasma testosterone levels in transwomen and was not associated with worsening lipid profile, was effective, and well tolerated in transwomen regardless of their age and may be considered an adjunct to the ant-androgen and estrogen therapy.