Leptin

Overview

Leptin measures a hormone primarily secreted by adipose tissue that circulates bound to proteins and signals the hypothalamus to regulate energy balance and appetite. It inhibits hunger and promotes energy expenditure; resistance to leptin signaling is common in obesity despite high circulating levels. Elevated leptin indicates obesity or leptin resistance; low levels suggest lipodystrophy or malnutrition. Clinically, leptin assessment aids diagnosis of rare genetic obesity syndromes and evaluates hypothalamic-pituitary dysfunction.

Clinical Use Cases

  • Diagnosing congenital leptin deficiency and lipodystrophy syndromes.
  • Evaluating hypothalamic amenorrhea and energy-deficiency states.
  • Research assessment of obesity pathophysiology and leptin resistance.
  • Monitoring recombinant leptin therapy response in deficiency states.

Specimen Types

  • Serum.
  • Plasma (EDTA or heparin).

Measurement Methods

  • Radioimmunoassay (RIA).
  • Enzyme-linked immunosorbent assay (ELISA).
  • Electrochemiluminescent immunoassay.

Test Preparation and Influencing Factors

  • Fasting sample preferred; levels decrease postprandially.
  • Obesity, insulin resistance, and inflammation elevate leptin.
  • Estrogens increase leptin; testosterone decreases leptin.
  • Sleep deprivation or stress transiently affect circulating leptin.

Synonyms

  • Obese gene protein.
  • LEP.
  • Obesity factor.

Further Reading