Hypothalamic-Pituitary Hormones and Obesity

Hypothalamic-pituitary growth hormone, thyroid, cortisol, and sex steroid axes can directly regulate adipocyte, muscle, and bone function. These anterior pituitary hormonal systems are important in normal growth and development, including the expression of sexual dimorphic differences in body composition, adiposity, and body fat distribution. Recent studies have also demonstrated a role for the posterior pituitary hormone oxytocin in weight regulation. States of hormonal deficiency and excess production can impact adiposity and adiposity-related complications. Other than hypothyroidism, however, disruptions of hypothalamic-pituitary axes are uncommon and rarely considered to be causal of obesity. On the other hand, obesity can have secondary effects on pituitary function that mimic deficiency states, making interpretation of screening tests challenging in patients with obesity. This chapter will provide an overview of normal hypothalamic-pituitary functions, their roles in regulating body composition and glucolipid metabolism, and recommend screening approaches to differentiate primary dysfunctional states from secondary effects of increased adiposity.