Amenorrhea may be caused by pregnancy, menopause or premature ovarian failure, abnormalities or immaturity of the hypothalamic-pituitary-ovarian axis, inadequate nutrition, chromosomal abnormalities, and thyroid disorders. As women age, their ovarian reserve is depleted and they have fewer ovulatory cycles until menstruation stops completely, a phase of life referred to as menopause. Menopause is characterized by the lack of ovarian estrogen production, resulting in manifestations such as vaginal atrophy, hot flashes, and night sweats. Sleep disturbances and mood changes may also be present. While menopause has a median age of onset of about 50 years old, symptoms can begin much earlier than that in some patients. Menopause before age 45 years is referred to as early menopause, whereas menopause occurring before age 40 years is often caused by primary ovarian insufficiency. Younger patients who present with signs of menopause such as irregular menses should first be evaluated with measurement of serum B-hCG concentration to rule out pregnancy as the underlying cause of their symptoms. This is especially pertinent for this patient with a slightly enlarged uterus, which may be caused by pregnancy.
A GnRH agonist (eg, leuprolide) is used as continuous therapy to treat central precocious puberty, not pubertal delay, by inhibiting gonadotropin release. It can also be used as pulsatile therapy in the treatment of functional hypothalamic amenorrhea, but this condition is typically due to insufficient caloric intake to meet nutritional needs (eg, anorexia nervosa), which is unlikely in this patient with a normal BMI.
Evaluation includes a thyroid-stimulating hormone level to evaluate for hypothyroidism and a pelvic ultrasound to confirm the presence of a uterus and ovaries. MRI of the brain may be indicated in a patient who also has galactorrhea and an elevated prolactin level, a presentation suggestive of a prolactinoma.
MRI of the head is indicated in patients with a low or normal FSH, high prolactin, or visual field defects to evaluate hypothalamic and pituitary causes (eg, sellar mass).