Amenorrhea

Amenorrhea is the absence of menstrual periods. Primary amenorrhea is the failure to begin menses by age 15 with normal secondary sexual development, or by age 13 without secondary characteristics. Secondary amenorrhea is the absence of menses for three consecutive cycles or for at least six months in someone who has previously menstruated.

Causes of amenorrhea are diverse and commonly grouped by mechanism. Pregnancy and lactational amenorrhea are physiologic causes that must be excluded first. Hypothalamic or pituitary problems include functional hypothalamic amenorrhea from stress, weight loss, or excessive exercise; hyperprolactinemia from pituitary adenomas or medications; and other pituitary disorders. Ovarian causes include premature ovarian insufficiency, anovulation related to polycystic ovary syndrome, and gonadal failure. Uterine or anatomic factors such as Asherman syndrome (intrauterine adhesions) or congenital anomalies can produce primary or secondary amenorrhea. Endocrine and metabolic problems such as thyroid disease or severe systemic illness may contribute. Medications, including dopamine antagonists, opioids, and some chemotherapeutic agents, can disrupt menses. In many cases, especially secondary amenorrhea, the underlying cause is a combination of hormonal, nutritional, and lifestyle factors.

Evaluation begins with exclusion of pregnancy, followed by history and physical examination to assess secondary sexual characteristics and signs of illness. Laboratory testing typically includes pregnancy testing, serum FSH and LH, estradiol, prolactin, and TSH; additional tests may include androgens, cortisol, and imaging such as pelvic ultrasound, with MRI if pituitary disease is suspected.

Management targets the underlying cause and may include nutritional rehabilitation, lifestyle modification, hormonal therapy to protect bone health or regulate cycles, treatment of thyroid or prolactin abnormalities, or surgical intervention for structural disorders. Prognosis varies with cause; many cases improve with appropriate treatment, while premature ovarian insufficiency is often permanent.