Article
Leptin
Leptin is a peptide hormone secreted predominantly by white adipose tissue; circulating levels reflect total energy (fat) stores.
Pubertal Role
Acts as a permissive signal to the hypothalamus indicating adequate energy reserves for reproductive maturation. Severe leptin deficiency or very low body fat (e.g., in hypothalamic amenorrhea, anorexia) can delay puberty or disrupt menstrual function.
Mechanism
- Binds leptin receptors (Ob-R) in hypothalamic nuclei influencing KNDy neuron activity and GnRH pulsatility.
- Interacts with insulin and IGF-1 signaling; modulates neuropeptide Y and pro-opiomelanocortin pathways affecting energy balance.
Clinical Notes
- Congenital leptin deficiency: delayed or absent puberty, hypogonadotropic hypogonadism reversible with replacement.
- Obesity: Elevated leptin with central leptin resistance; may correlate with earlier pubertal timing in girls.