THU227 Isosexual Peudo-precocious Puberty Due To Leydig Cell Tumor In A Prepubertal Child

Disclosure: M. Baby: None. A. Xu: None. N. Shacham: None. E. Shapiro: None. B.C. Shah: None. Background: Testicular tumors account for 2-4% of all childhood cancers. Leydig cell tumors are the most common form of sex cord stromal tumors and represent 1-3% of all testicular tumors. In the pediatric population, testicular Leydig cell tumors present with signs of precocious puberty. Workup reveals low gonadotropins with elevated testosterone and testicular mass on ultrasound. Treatment involves surgical enucleation (partial orchiectomy) in most cases. Clinical case: We present the case of a 4 year 10 month old male who presented to endocrine clinic for precocious puberty. He developed pubic hair three months prior with body odor. He did not have any CNS symptoms including headaches or visual changes. There was no use of exogenous androgens at home. He was born full term, small for gestational age with an uncomplicated postnatal course. There was no family history of precocious puberty. Height was at the 99th percentile (z-score 2.7), weight 98th percentile (z-score 2.07), and BMI 86th percentile (z-score 1.09). On exam, he was lean and appeared muscular. His testes were asymmetrical with the right testicle measuring 3 ml and the left testicle 2 ml. Scrotal hair was curly and sparse, Tanner III. Stretched penile length was 7 cm (90(th) percentile), width was 3.2 cm. Results: Bone age was advanced to 10 year 0 months with height age of 7 year 3 months. Serum gonadotropins were low, testosterone was pubertal at 115 ng/dl (Electrochemiluminescence Immunoassay). Serum 17-hydroxyprogesterone (221 ng/dl, ref range 0-90 ng/dl) androstenedione (163 ng/dl, ref range = < 51 ng/dl), and IGF-1 (368 ng/ml, ref range 108 – 293 ng/ml) were elevated. ACTH, cortisol, thyroid profile, and prolactin were normal. Beta-HCG and AFP were negative. ACTH stimulation test showed normal response. Testicular ultrasound with doppler was performed; right testicle measured 1.82 x 1.06 x 1.36 cm, volume of 1.4 ml, while left measured 1.27 x 0.72 x 0.87 cm, 0.4 ml. Within the right testicle, there was a mass that was hypoechoic, vascular (with a testicular artery feeding branch in the periphery), multinodular and measured 1.2 x 0.8 x 1.10 cm (0.53 ml). He was referred to urology and underwent enucleation of the right testicular mass through an inguinal approach. Grossly, the mass appeared tan and lobulated and surgical pathology confirmed a benign Leydig cell tumor. The patient recovered well and post-operative serum testosterone level at 2 weeks was <2.5 ng/dl. Conclusion: We present a case of a testicular Leydig cell tumor that presented as peripheral precocious puberty marked by low gonadotropins and elevated testosterone with ultrasound findings of a vascular mass with testicular artery feeding branch in the periphery. Early detection of a Leydig cell tumor is crucial as it can be treated by enucleation thus salvaging the testes. Presentation: Thursday, June 15, 2023