Infrequent Menstruation

Infrequent menstruation is bleeding that comes less often than every 38 days, but at least once in 90 days, in a woman who is not pregnant.

It results from infrequent ovulation (polycystic ovary syndrome, perimenopause, hypothalamic suppression), thyroid disease, hyperprolactinaemia, hormonal contraception (levonorgestrel intrauterine system, implant, depot injection) and early ovarian insufficiency.

It matters because long gaps without a bleed expose the endometrium to unopposed oestrogen, with a risk of hyperplasia, and it may reflect infertility or bone loss.

• Risk factors: obesity, polycystic ovary syndrome, low body weight, intense exercise, thyroid disease, perimenopause, progestogen-only contraception.
• Cycles between 38 and 90 days are infrequent; no bleed for 90 days or longer is amenorrhoea.
• A bleed at least every 3 months protects the endometrium.

Women report long gaps between periods, with heavy or prolonged bleeding when a period arrives. Signs depend on the cause: hirsutism and acne, weight gain, goitre, galactorrhoea, hot flushes or weight loss.

• Menstrual diary showing intervals longer than 38 days.
• Body mass index, hirsutism score and waist circumference.
• Differential diagnosis: polycystic ovary syndrome, hypothyroidism, hyperprolactinaemia, hypothalamic amenorrhoea, perimenopause, premature ovarian insufficiency, contraceptive effect, pregnancy, ovarian or adrenal tumour, Cushing syndrome.
• Complications: endometrial hyperplasia and cancer, infertility, heavy breakthrough bleeding, type 2 diabetes, low bone density, anxiety about fertility.

The approach is to exclude pregnancy and to find the cause of infrequent ovulation.

• Urine or serum hCG; menstrual diary; weight, height, blood pressure, hirsutism score.
• Thyroid stimulating hormone, prolactin, follicle stimulating hormone, luteinising hormone, oestradiol, total testosterone, sex hormone binding globulin.
• Pelvic ultrasound (ovarian volume above 10 mL or 12 or more follicles of 2 to 9 mm; endometrial thickness above 12 mm needs sampling); fasting glucose, lipids.
• Endometrial sampling if age is 45 years or above, or if there are risk factors such as obesity and long periods of amenorrhoea.

The principle is to treat the cause and to give a progestogen at least every 3 months to protect the endometrium.

• Supportive: weight loss of 5 to 10 percent if overweight; regular exercise of 150 minutes weekly; weight gain if underweight; stress management; menstrual diary; fertility counselling.
• Pharmacological: medroxyprogesterone 10 mg oral once daily for 10 to 14 days every 1 to 3 months to induce a withdrawal bleed; combined oral contraceptive pill with ethinylestradiol 30 micrograms and levonorgestrel 150 micrograms oral once daily for 21 days then 7 days free; levonorgestrel intrauterine system 52 mg for 5 years; metformin 500 mg oral once daily increased weekly to 500 mg 3 times daily (maximum 2000 mg daily) for insulin resistance; levothyroxine 50 micrograms oral once daily increased every 4 to 6 weeks to normalise thyroid stimulating hormone; cabergoline 0.25 mg oral twice weekly increased to a maximum of 1 mg twice weekly for hyperprolactinaemia; for pregnancy wish: letrozole 2.5 mg oral once daily on days 3 to 7, increased by 2.5 mg each cycle to 7.5 mg, or clomifene 50 mg oral once daily on days 2 to 6, increased to 100 and 150 mg.
• Procedures: endometrial sampling or hysteroscopy for thick endometrium; laparoscopic ovarian drilling for polycystic ovary syndrome resistant to drug induction.
• Special groups: women with implants or depot injection expect infrequent bleeding and are reassured when examination is normal; women who cannot use oestrogen (migraine with aura, hypertension, previous clot, smoking above age 35 years) use progestogen-only methods; women wishing to conceive stop the contraceptive pill and take folic acid 400 micrograms oral daily from 3 months before conception.
• Red flags: endometrial thickness above 12 mm, bleeding after long amenorrhoea that is heavy, rapid virilisation, visual loss with high prolactin, weight loss, age above 45 years with new pattern.
• Follow-up: review at 3 months with diary; yearly review of weight, glucose and lipids in polycystic ovary syndrome; endometrial assessment if fewer than 3 bleeds a year without treatment.