While we have found that the LH response to GnRHa is generally sufficient to confirm the diagnosis of CPP in the great majority of boys for their consistent increase in LH secretion at stage T2 (23, 48), the T response can be confirmatory and useful in atypical cases of sexual precocity, as described in the vignette from our clinic (see Box 1). The gene discussed is PLOD1; the disease is central precocious puberty.