Endocrine Disorders Causing Menstrual Irregularities

Introduction to Endocrine Causes

The primary endocrine disorders causing menstrual irregularities are polycystic ovary syndrome (PCOS), thyroid dysfunction, hyperprolactinemia, hypothalamic amenorrhea, premature ovarian failure, and Cushing's syndrome, as identified by the American College of Obstetricians and Gynecologists 1, 2, 3

Hyperprolactinemia causes anovulation by inhibiting gonadotropin secretion via suppression of kisspeptin, resulting in oligomenorrhea, amenorrhea, or polymenorrhea, according to the Endocrine Society 1, 2
Primary hypothyroidism causes menstrual irregularities in a substantial proportion of affected women, with hyperprolactinemia occurring in 43% of women with frank hypothyroidism and 36% with subclinical hypothyroidism, as reported by the American Thyroid Association 2, 3
Menstrual cycles typically normalize within 2-5 days of achieving adequate thyroid hormone replacement with levothyroxine, as stated by the American Association of Clinical Endocrinologists 3
Hypothalamic amenorrhea is characterized by disturbed gonadotropin secretion with low LH levels, causing amenorrhea or oligomenorrhea without signs of hyperandrogenism, according to the European Society of Human Reproduction and Embryology 6, 5
Premature ovarian failure presents with amenorrhea and FSH values above 50 mIU/L in women under age 40, occurring in approximately 4% of women with certain neurological conditions, as identified by the American College of Obstetricians and Gynecologists 1, 6

Measure TSH and free T4 immediately to exclude thyroid dysfunction, as this is a common and readily treatable cause of menstrual irregularities, recommended by the American Thyroid Association 2, 3
Check prolactin levels with morning resting samples to exclude hyperprolactinemia, as suggested by the Endocrine Society 2
Obtain pregnancy test in all reproductive-age women regardless of reported contraceptive use, as recommended by the American College of Obstetricians and Gynecologists 3

Measure total testosterone, free testosterone, androstenedione, and DHEA-S to characterize the androgen profile in women with suspected PCOS, as recommended by the American College of Obstetricians and Gynecologists 2, 4
Obtain LH and FSH levels between days 3-6 of the menstrual cycle to evaluate for PCOS, with LH/FSH ratio >2 suggestive of PCOS, according to the Endocrine Society 2, 4

Certain antiepileptic drugs can cause or worsen menstrual irregularities through multiple mechanisms, including direct effects on hypothalamic-pituitary axis, peripheral endocrine gland effects, altered hormone metabolism, and drug-induced weight changes, as reported by the American Academy of Neurology 7, 1, 6, 3
Valproate is particularly associated with PCOS development, with 45% of women on valproate monotherapy experiencing menstrual irregularities, according to the European Society of Human Reproduction and Embryology 6