Evaluation and Management of Late Menstrual Periods

Initial Evaluation

A late menstrual period with negative pregnancy tests most commonly indicates ovulatory dysfunction, but requires systematic evaluation to exclude pregnancy, thyroid disorders, hyperprolactinemia, and polycystic ovary syndrome (PCOS), according to the American College of Obstetricians and Gynecologists 1

Thyroid function tests (TSH, free T4) should be performed to exclude thyroid dysfunction, which commonly presents with menstrual irregularity, as recommended by the Endocrine Society 1
Prolactin level should be measured to rule out hyperprolactinemia, which suppresses GnRH pulsatility and causes anovulation mimicking PCOS, with confirmation of elevation using 2-3 morning resting samples taken 20-60 minutes apart, as suggested by the American College of Obstetricians and Gynecologists 1, 2
FSH and LH should be measured between cycle days 3-6, with three estimations 20 minutes apart for accuracy, and an LH/FSH ratio >2 suggests PCOS, according to the American Society for Reproductive Medicine 1, 3

Polycystic ovary syndrome (PCOS) is characterized by clinical features such as oligomenorrhea, hyperandrogenism, and obesity, with laboratory findings including LH/FSH ratio >2, elevated free testosterone, and low mid-luteal progesterone indicating anovulation, as defined by the American College of Obstetricians and Gynecologists 1, 3
Hyperprolactinemia inhibits gonadotropin secretion by suppressing kisspeptin neurons, directly blocking GnRH pulsatility and causing anovulation, and treatment priority should be to address primary hypothyroidism first, as recommended by the Endocrine Society 2

Medical treatments such as progestin-only contraception or combined hormonal contraception may be used for abnormal uterine bleeding associated with ovulatory dysfunction, as recommended by the American Academy of Family Physicians 4
Metformin may be used for insulin resistance if fasting glucose/insulin ratio >4, particularly in PCOS, as suggested by the American College of Obstetricians and Gynecologists 2

Failing to screen for thyroid disorders and hyperprolactinemia before attributing symptoms to PCOS, as recommended by the Endocrine Society 1, 2
Not accounting for medication effects on menstrual patterns, such as antipsychotics and depot medroxyprogesterone acetate, as warned by the Infectious Diseases Society of America and the American College of Obstetricians and Gynecologists 2, 5