Idiopathic gonadotropin-independent precocious puberty - is regular surveillance required?

Context Germ cell tumours (GCTs) secreting β-human chorionic gonadotropin (β-HCG) are a rare cause of gonadotropin-independent precocious puberty (GIPP). Case description A 5.7-year-old boy presented with GIPP. Investigations to elucidate the underlying cause revealed elevated serum β-HCG. Ultrasound of the abdomen and testes, urine steroid profile, bone isotope scan, and sequencing of the luteinizing hormone receptor gene (LHCGR) were normal. Despite paired serum and cerebrospinal fluid β-HCG measurement suggesting local (brain) β-HCG production, repeated magnetic resonance imaging (MRI) of the brain as well as MRI of the mediastinum did not identify a tumour source of persistently elevated serum β-HCG. Treatment with cyproterone acetate and spironolactone was unsuccessful. Increase in testicular volumes prompted the addition of a gonadotropin releasing hormone (GnRH) analogue. Due to progressing virilisation and skeletal maturation, treatment was changed to a combination of anastrozole and bicalutamide at the age of 7 years. One year later, serum β-HCG and testosterone concentrations spontaneously normalised followed by reductions in the height velocity, skeletal maturation and virilisation. The proband achieved his genetic height potential. No medication side effects were observed. The patient subsequently presented with non-secreting pineal GCT at 14 years, 8½ years after his initial presentation with GIPP. Conclusions Our case highlights that GIPP with no definite underlying aetiology at diagnosis should be considered as a prodrome for GCTs, and regular radiological surveillance for earlier tumour identification is warranted. To the best of our knowledge, our case is the first reported case of the use of anastrozole and bicalutamide in the setting of idiopathic GIPP. The good height outcome in our case warrants the trial of anastrozole and bicalutamide in similar cases.