What hormone might a 19-year-old male be deficient in if he has not developed chest hair?

• A. Estrogen
• B. Testosterone
• C. Growth hormone
• D. Prolactin

Answer: (B)

Chest hair development in males is driven by androgens, primarily testosterone. During puberty, testosterone acts on hair follicles to produce terminal body hair in the chest, armpits, and other areas. If testosterone activity is low, those androgen-dependent features may be reduced or absent, so not having chest hair at 19 most naturally suggests deficient testosterone activity. The other hormones listed don’t play the same direct role in male chest hair: estrogen is more related to female secondary sexual traits and breast tissue effects in males, growth hormone influences overall growth rather than specific hair patterns, and prolactin governs lactation.