How are menstrual irregularities managed in patients with thyroid disorders?

Management of Menstrual Disorders in Thyroid Disease

Treat the underlying thyroid disorder first—normalizing thyroid function resolves menstrual irregularities in most patients, with levothyroxine restoring regular cycles in approximately 59% of hypothyroid women with amenorrhea within 6 months. 1, 2

Initial Diagnostic Evaluation

Confirm Thyroid Dysfunction and Rule Out Other Causes

• Measure TSH and free T4 to confirm the diagnosis and severity of thyroid disease 3, 1
• Obtain a pregnancy test (mandatory in all reproductive-age women regardless of reported contraceptive use) 4
• Check prolactin levels, as hypothyroidism can cause hyperprolactinemia and galactorrhea through TRH-mediated prolactin release 3, 5
• Measure LH, FSH (day 3-6 of cycle), and mid-luteal progesterone (<6 nmol/L indicates anovulation) to assess ovulatory status 3, 6
• Consider pelvic ultrasound (transvaginal preferred) if hormonal tests suggest ovarian pathology or to exclude structural causes (polyps, fibroids, adenomyosis) 3, 4
• Perform endometrial biopsy in women >35 years with irregular bleeding to exclude hyperplasia or malignancy before initiating treatment 4

Document Menstrual Pattern Specifics

• Maintain a menstrual chart for at least 6 months documenting cycle length, duration, and flow 3
• Hypothyroidism most commonly presents with hypermenorrhea (heavy bleeding) and polymenorrhea (frequent bleeding), occurring in 33% of overt hypothyroid patients versus 6% of controls 7, 8, 5
• Hyperthyroidism typically causes oligomenorrhea (infrequent periods) and hypomenorrhea (light bleeding), though menstrual disturbances occur in only 21.5% of thyrotoxic patients in recent series 8, 5

Treatment Algorithm

Primary Treatment: Thyroid Hormone Replacement for Hypothyroidism

Initiate levothyroxine at 1.6 mcg/kg/day for patients without cardiac risk factors (age <70, no cardiac disease, not frail). 9

• For patients >70 years or with cardiac disease/multiple comorbidities, start at 25-50 mcg daily and titrate upward 9
• Monitor TSH every 6-8 weeks after any dosage change until stable, then every 6-12 months 9
• Target TSH within the normal reference range (0.4-4.5 mIU/L) 3, 9
• Menstrual cycles typically normalize within 2-5 days of achieving adequate thyroid hormone replacement, with complete resolution of heavy bleeding within one week 10
• Serum testosterone levels decrease with levothyroxine treatment, which may contribute to menstrual cycle restoration 2

Management of Persistent Heavy Bleeding During Thyroid Treatment Titration

If heavy bleeding persists while optimizing thyroid replacement:

First-line: NSAIDs during menstruation

• Mefenamic acid 500 mg three times daily for 5 days during bleeding episodes 1, 6, 4
• Alternative: Celecoxib 200 mg daily for 5 days 6, 4
• Multiple NSAIDs (indomethacin, flufenamic acid, diclofenac) demonstrate statistically significant reductions in menstrual blood loss 3, 6
• Avoid aspirin—it may increase blood loss in women with baseline menstrual blood loss <60 mL 3, 6

Second-line: Tranexamic acid (if NSAIDs fail)

• Significantly reduces menstrual blood loss compared to placebo 3, 6
• Contraindicated in women with active thromboembolic disease or history/risk of thrombosis 3, 6

Third-line: Short-term hormonal therapy

• Low-dose combined oral contraceptives for 10-20 days if medically eligible and no contraindications 1, 4
• Note: Combined oral contraceptives increase venous thromboembolism risk 3-4 fold 4

Long-term option: Levonorgestrel-releasing IUD

• Most effective long-term approach, reducing menstrual blood loss by 71-95% 6, 4
• Gold standard when estrogen is contraindicated 4

Management of Oligomenorrhea/Amenorrhea in Hyperthyroidism

• Treat the underlying hyperthyroidism with antithyroid medications, radioactive iodine, or surgery as indicated 8
• Radioactive iodine (¹³¹I) therapy does not cause reduced fecundity or loss of fertility and carries minimal genetic hazard 8
• Menstrual cycles typically normalize with restoration of euthyroid state 8, 5

Special Considerations and Pitfalls

Pregnancy and Fertility

• Both hyperthyroidism and hypothyroidism reduce fertility and increase risk of abortion, stillbirth, and prematurity 8, 5
• For pregnant patients with pre-existing hypothyroidism, increase levothyroxine by 12.5-25 mcg/day as soon as pregnancy is confirmed 9
• Monitor TSH every 4 weeks during pregnancy and maintain in trimester-specific reference range 9
• Return to pre-pregnancy levothyroxine dose immediately after delivery 9

Coagulation Abnormalities in Severe Hypothyroidism

• Severe hypothyroidism can cause acquired von Willebrand syndrome, shifting the hemostatic system toward a hypocoagulable and hyperfibrinolytic state 10, 5
• This contributes to increased bleeding risk and menorrhagia 10, 5
• Coagulation parameters normalize with levothyroxine replacement 10

Medication Interactions

• Certain antiepileptic drugs (valproate, carbamazepine, phenytoin) can worsen menstrual irregularities and affect SHBG levels 3, 6
• Review all medications that may impact reproductive hormones 3

When Menstrual Irregularities Persist Despite Euthyroid State

• Reassess for structural pathology (polyps, fibroids, adenomyosis, endometrial hyperplasia) 3, 4
• Evaluate for PCOS (affects 4-6% of women): check LH/FSH ratio (>2 suggests PCOS), testosterone (>2.5 nmol/L), and pelvic ultrasound for >10 peripheral cysts of 2-8 mm diameter 3, 1, 6
• Consider other causes of anovulation: hyperprolactinemia, hypothalamic dysfunction, premature ovarian failure 3
• Refer to gynecology if bleeding persists despite two treatment attempts 4

Monitoring Response to Treatment

• Reassess menstrual pattern within 1-2 cycles of initiating symptomatic bleeding management 1, 4
• Continue monitoring TSH every 6-12 months once stable on thyroid replacement 9
• Refer to endocrinology if thyroid dysfunction is confirmed or if complex endocrine abnormalities are identified 1
• Refer to reproductive endocrinology if infertility persists (inability to conceive after 12 months of unprotected intercourse with male factors excluded) 3, 1