SAT-101 The Booster Effect of Aromatase Inhibitor to Overcome Waning Effect of Recombinant Human Growth Hormone

Aromatase inhibitor (AI) is a drug that blocks the conversion of androgens to estrogens, originally approved by FDA as a treatment of breast cancer in postmenopausal women. In several studies, it has been proposed that AI appears effective to improve the final adult height especially combined with rhGH therapy, by delaying growth plate closure. Patients treated with rhGH showed highest growth rate during the first year of treatment, with an average increase of 8–10 cm per year (often called “catch-up” growth), however, followed by a progressive decrease in growth rate over the next several years, which is called “waning effect” of rhGH. In this report, we would like to introduce 2 cases of short pubertal boys showing booster effect of AI when co-treated with rhGH, to overcome waning effect of rhGH and improve the final adult height. Case 1. A boy at the age of 8 years and 1 month visited out clinic with short stature. His height was 118cm (4%), weight was 19.2kg (0%). His MPH was calculated as 173cm. Bone age was 6.9 years by the TW3 method. Initial laboratory finding showed no other abnormal findings including normal IGF-1 levels, so we diagnosed the patient as idiopathic short stature (ISS), and started rhGH treatment. During the rhGH treatment of 4 years and 9 months, the patient obtained additional 30.7cm growth to 148.7cm (23%). However, the patient showed decreased growth velocity of 2.2 cm in the last 6 months, which was thought to be “waning effect” of rhGH. The patient and his parents wanted to improve his height using AI, and after taking agreement about the drug, we added AI. During the combined treatment of 1 year and 10 months, his height was improved to 164.9cm (32%) with a gain of 16.2cm, and no adverse reaction was observed. Case 2. A 8 years and 2 months-old boy visited out clinic with short stature. His height was 116.3cm (0%) and weight was 22.6kg (14%). There have been no unusual findings in past history and family history. His MPH was calculated as 165.9cm. Bone age was 8.2 years by the TW3 method. He was also diagnosed as ISS, and started rhGH treatment. During 5 years and 1 month of rhGH treatment, the patient obtained additional 33.3cm growth to 149.6cm (17%). However, the patient showed progressive decreased growth velocity of 3.3 cm in the last 6 months, so we added AI treatment, and after the combined treatment of 1 year and 5 months, his height was 161.6cm (23%). After that, his parents wanted to quit AI, so we maintained only rhGH treatment for 7 months, and his final height was checked as 167cm. In our cases, we suggest that the additional use of AI to patients with progressive decreased growth rate during previous years of GH treatment can improve growth velocity again, and increase the final adult height with successful bone age suppression, which has not been reported before. Therefore, AI could be expected as effective booster drug to overcome waning effect of rhGH.