USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which hormone(s) play a role in the synthesis of surfactant in the lungs?

1. Insulin

2. Cortisol and Thyroxine

3. Growth hormone

4. Epinephrine

The correct answer is: Cortisol and Thyroxine

The synthesis of surfactant in the lungs is significantly influenced by cortisol and thyroxine. Cortisol, a glucocorticoid hormone produced by the adrenal cortex, plays a crucial role in stimulating the production of surfactant by type II alveolar cells in the lungs. This surfactant reduces surface tension within the alveoli, preventing their collapse during exhalation and facilitating proper lung expansion and gas exchange. Thyroxine, a thyroid hormone, also supports lung development and can enhance surfactant production. The presence of these hormones is particularly important during late gestation; they help prepare the lungs for functioning after birth, where adequate surfactant levels are essential to maintain alveolar stability. The other hormones listed do not have a direct role in the synthesis of surfactant. Insulin primarily regulates glucose homeostasis, growth hormone influences growth and metabolism but does not directly affect surfactant production, and epinephrine is involved in the stress response and bronchodilation rather than surfactant synthesis. Thus, the correct answer reflects the significant contributions of cortisol and thyroxine in surfactant production and lung maturation.