Precocious puberty and unlicensed paediatric drugs for severe hyperparathyroidism.

Puberty is often delayed in children with chronic kidney disease. A 5-year-old boy suffering from severe chronic kidney disease due to a mutation in the TCF2 gene presented with a clinical precocious peripheral puberty 3 weeks after introducing cinacalcet and 2 months after introducing lanthanum carbonate. A retrospective measurement of serum sexual and adrenal hormones before the introduction of cinacalcet but after the introduction of lanthanum carbonate revealed an asymptomatic biological underlying precocious puberty. With more than 1-year follow-up, the aetiology of this precocious puberty remains unexplained. Cinacalcet can be responsible for hypotestosteronaemia in adults, but no case of precocious puberty has been described in association with cinacalcet so far. Natural lanthanides can activate in vitro the calcium sensor receptor, but there are no clinical data about side effects of lanthanum carbonate on sexual hormones. An unknown phenotype of TCF2 mutation may also be discussed. Monitoring of plasma testosterone in patients receiving unlicensed paediatric drugs for managing hyperparathyroidism and presenting with a change in genitals is therefore recommended.