Final answer:
H2 receptor antagonists can cause gynecomastia and galactorrhea by indirectly affecting hormonal balances, including potentially elevating prolactin levels, which regulate mammary gland development and milk production.
Step-by-step explanation:
The H2 receptor antagonist in question that can cause gynecomastia (male breasts) and galactorrhea (milk leakage) does so by impacting hormonal balances, especially by potentially increasing prolactin levels. This happens because H2 antagonists can interfere with the production of stomach acid and have various systemic effects due to their action on H2 receptors, which might include altering the endocrine system indirectly.
Normally, testosterone and other hormones regulate processes such as the development of mammary tissue and milk production. If an antagonist molecule binds to and blocks plasma membrane receptors that testosterone interacts with, this can disrupt normal hormonal functions, potentially leading to side effects like gynecomastia and galactorrhea, as testosterone might become less effective at inhibiting these effects. Actions on brain receptors, like 5-HT2 receptors mentioned in the reference, can also have indirect effects on hormone secretion and consequent physical changes.
Overall, while H2 receptor antagonists are not directly linked to prolactin levels, through complex hormonal pathways, they can possibly contribute to gynecomastia and galactorrhea by altering the hormonal balance.