For all these reasons, we think that, for the diagnosis of CPP in girls, the LH response to stimulation, rather than in absolute values, needs to be interpreted in conjunction with the other clinical, radiological and hormonal parameters, including the sex-hormone response to GnRHa stimulation (discussed below), and, as importantly, an observation period of 3–6 months to evaluate progression in cases that are not clear-cut. This evidence concerns the gene PLOD1 and central precocious puberty.