Volume 21, Number 4Case ReviewUsing 17-OHP as Serum Biomarker to Monitor Therapy in Patients With Hypogonadotropic HypogonadismA MouzannarM NarasimmaP PatelR RamasamyExogenous testosterone administration decreases intratesticular testosterone (ITT) significantly, an essential hormone for spermatogenesis. Therefore, treatment of patients with hypogonadotropic hypogonadism (HH) who desire infertility can be challenging. These patients are treated with recombinant follicle-stimulating hormone (FSH), clomiphene citrate, and human chorionic gonadotropin (hCG) to increase their ITT. However, there is no approved serum biomarker for ITT and it can only be measured via invasive testicular biopsy or aspiration. Previous authors have speculated that serum 17-hydroxyprogestrone (17-OHP) can be used as serum biomarker for ITT. In our case report, we demonstrate increase in 17-OHP associated with spermatogenesis after commencing treatment for infertility in patient with HH. [Rev Urol. 2019;21(4):180–182] © 2020 MedReviews®, LLCBiomarkerInfertility17-HydroxyprogesteronIntratesticular testosteroneHypogonadotropic hypogonadism