Which medical condition is associated with a decrease in milk supply?

Thyroid dysfunction is known to influence various aspects of metabolism and hormonal balance in the body, which can extend to lactation. Specifically, conditions such as hypothyroidism can lead to a decrease in milk supply. The thyroid hormones play a critical role in breast development and the production of milk. Insufficient levels of these hormones can lead to reduced milk production, making it difficult for mothers to maintain adequate breastfeeding.

In contrast, while hypertension, diabetes mellitus, and autoimmune disorders can certainly pose complications during pregnancy and the postpartum period, their direct effects on milk supply are not as clearly established. For instance, while diabetes can have metabolic effects, it is not universally linked to decreased milk production in the same way that an imbalance in thyroid hormones is. Thus, thyroid dysfunction stands out as the condition most directly associated with a decrease in milk supply.