What effect does hypothyroidism have on prolactin levels?

Hypothyroidism is known to increase prolactin levels. The mechanism behind this involves the intricate interplay between the hypothalamus, pituitary gland, and thyroid function. In a state of hypothyroidism, there is an increase in the levels of thyroid-releasing hormone (TRH), which is produced by the hypothalamus. Elevated TRH stimulates the pituitary gland to secrete more prolactin. Therefore, when thyroid hormone levels are low, the feedback loop fails, resulting in an increase in prolactin production.

Clinical observations support this relationship, as patients with hypothyroidism often present with elevated levels of prolactin. This increase can lead to various symptoms, including galactorrhea (milk production), irregular menstrual cycles in women, and fertility issues in both sexes. Understanding this connection is important for clinicians, as they must consider thyroid function in patients presenting with elevated prolactin levels to avoid misdiagnosis of conditions like prolactinoma, which could lead to unnecessary interventions.