Testotoxicosis: current viewpoint

Testotoxicosis is a form of gonadotropin-independent (peripheral) precocious puberty in which boys experience early onset and progression of puberty. Patients have accelerated growth, early development of secondary sexual characteristics and usually reduced adult height. Testotoxicosis is caused by an activating mutation of the luteinizing hormone (LH) receptor, leading to increased levels of sex steroids in the context of low LH. Therapy has, therefore, traditionally targeted steroidogenesis. However, the drugs used have been associated with side effects. More recently, a combination of an oral anti-androgen (spironolactone) and an aromatase inhibitor (testolactone) decreased height velocity and improved predicted height. A phase II study in testotoxicosis is currently underway,exploring the combination of a highly selective anti-androgen, bicalutamide, and the potent aromatase inhibitor, anastrozole. These agents are well tolerated in the populations in which they have been studied and effectively inhibit testosterone activity and estrogen production, in adult patients.