Is neuropeptide Y responsible for constitutional delay of puberty in girls? A preliminary report

Abstract

Constitutional delay of puberty (CDP) in otherwise healthy girls is defined as failure to develop secondary sexual features past the age of 13 years (two standard deviations above the mean age at which secondary sexual features appear in the population of girls). The inhibitory action of neuropeptide Y (NPY) on the gonadotropic and somatotropic systems in experimental animals and stimulation by NPY of the hypothalamic–pituitary–adrenal axis have been reported, prompting us to study the levels of NPY, insulin-like growth factor-I (IGF-I) and cortisol in eight girls with CDP and normal weight (body mass index (BMI) 21.7 ± 4.5 kg/m2). The results were compared with those from a group of 40 girls (BMI = 20.0 ± 3.1 kg/m2) who demonstrated a normal course of puberty (NP). All girls were studied at menarche (mean age at menarche, study vs. control: 16.4 ± 0.7 vs. 12.6 ± 0.9 years). To measure NPY and IGF-1 we used a radioimmunoassay method, whereas cortisol was measured with an enzyme immunoassay. Blood was collected between 08.00 and 09.00 following an overnight fast. NPY was higher in girls with CDP (181.6 ±106.4 pg/ml) than in girls with NP (55.5 ± 26.3 pg/ml; p < 0.001). In the former group, cortisol was higher (397.3 ± 241.6 nmol/l) than in NP girls (142.7 ±98.0 nmol/l; p < 0.01). Levels of IGF-I in CDP girls were lower than in NP girls (558.0 ± 122.6 vs. 756.5 ± 226.8 ng/ml; p < 0.01). The results corroborate the involvement of NPY in sexual maturation and its role in delayed puberty.