A 42-year-old woman with unexplained nipple discharge has lost her libido. What is the most likely diagnosis?

The most likely diagnosis for a 42-year-old woman presenting with unexplained nipple discharge and loss of libido is hyperprolactinaemia. Elevated levels of prolactin can lead to galactorrhea (nipple discharge) and sexual dysfunction, particularly libido loss. This condition can arise due to a variety of causes, including prolactin-secreting pituitary tumors (prolactinomas), hypothyroidism, certain medications, and stress. The symptoms align with hyperprolactinaemia’s well-known effects on reproductive health, where increased prolactin inhibits gonadotropin-releasing hormone (GnRH) secretion, leading to lower levels of sex hormones that can manifest as reduced libido and breast discharge.

In contrast to this condition, Cushing's syndrome is characterized by excess cortisol which can lead to a range of symptoms including weight gain, hypertension, and hyperglycemia but is less directly associated with nipple discharge and libido changes as a primary symptom. Pheochromocytoma involves an adrenal tumor producing excess catecholamines, leading to symptoms related to adrenergic stimulation (palpitations, sweating, hypertension) rather than hormonal effects on lactation or libido. Hyperthyroidism can cause various symptoms such as weight