How the hormonal switch can change
Milk production depends on more than having breast tissue. The pituitary gland—a small hormone-producing organ beneath the brain—releases prolactin, which tells milk-making cells in the breast to produce milk. In most men, the hormonal environment keeps that signal too weak to start lactation, and the breast tissue remains minimally developed.
That balance can shift when the body is severely ill. The liver helps process and clear hormones; serious liver damage can disrupt that work and alter the balance of hormones that influence breast tissue. Extreme undernutrition can also disturb hormone regulation. If prolactin rises enough, the breast’s milk-making cells may respond, though this is unusual and depends on the person’s overall hormonal state and breast tissue.
A sign of a bigger problem
Milk from a man’s breast is not simply evidence that prolactin is high. Other causes can include medications or conditions affecting the pituitary, so clinicians consider the broader picture rather than treating the symptom as a diagnosis on its own. When lactation appears alongside severe illness or unexplained breast changes, it can be a clue to an underlying problem worth investigating.
The striking point is that lactation is not determined by sex alone: it depends on whether the right tissue receives the right hormonal signals.
