A comparison of patients with premature thelarche and idiopathic true precocious puberty in the initial stage of illness.

A comparative study of patients with premature thelarche and patients with idiopathic true precocious puberty was conducted. The age at the first visit tended to be lower for those with precocious puberty. In comparison with normative data for children, the frequency of low birthweight and small for date (SFD) status was greater in the 55 patients with premature thelarche, but SFD was also frequent in the 18 patients with precocious puberty. The height, weight and Kaup's index were all within the normal range for these two groups. The ratios for bone age/chronologic age and bone age/height age tended to be high in both groups. In the patients with premature thelarche, the blood luteinizing hormone (LH) level showed a normal response, and the blood follicle stimulating hormone (FSH) level a hyper-response, to stimulation with luteinizing hormone-releasing hormone (LH-RH). In contrast, both the blood LH and FSH levels showed a normal response to LH-RH stimulation in most of the patients with precocious puberty, and a hyper-response was rare among them. Although the blood estradiol (E2) level was higher in patients with precocious puberty than in those with premature thelarche, about 50% and 90% of the patients in the respective groups had normal levels. These results suggest that normal responses of blood LH and excessive responses of blood FSH to LH-RH loading may be useful in some patients for diagnosing premature thelarche at an early stage.