Naloxone-Induced Luteinizing Hormone Secretion in Normal, Precocious, and Delayed Puberty*

The aim of the present study was to evaluate the activity of opiate receptors involved in the control of LH secretion during pubertal development, as determined by the LH response to naloxone. Normal children (n = 28) of both sexes, subdivided according to breast (girls) or testicular (boys) development, and patients with idiopathic precocious puberty (n = 7), delayed puberty (n = 8), or hypergonadotropic hypogonadism (n = 4) were studied. Plasma LH levels were measured after the administration of naloxone (NLX; 0.08 mg/kg BW, iv), GnRH (50 micrograms, iv) or placebo. In healthy subjects, NLX significantly increased plasma LH levels only in girls and boys at the most advanced stage of gonadal maturation. NLX was ineffective in prepubertal and early pubertal children, and it did not significantly alter LH levels in children with delayed puberty or hypogonadism or in most of the children with precocious puberty. GnRH injection consistently increased plasma LH levels in healthy subjects as well as in the children with pubertal disturbances. These results indicate that the LH response to NLX occurs only at the most advanced stages of pubertal maturation when normal or precocious and is absent in early puberty or in children with pubertal disturbances. Furthermore, the results suggest that opioid regulation of LH secretion in humans changes during puberty, reaching an adult-like functional state with maturation of the hypothalamus-pituitary-gonadal axis.