Workup for Amenorrhea 6 Months After Stopping Birth Control
A woman with 6 months of amenorrhea after discontinuing hormonal contraception requires a systematic evaluation beginning with pregnancy exclusion, followed by measurement of FSH, LH, TSH, and prolactin levels to identify the underlying cause, which is most commonly pre-existing ovulatory dysfunction that was masked by contraceptive use. 1, 2
Initial Mandatory Testing
First, exclude pregnancy with a urine or serum pregnancy test—this is non-negotiable regardless of sexual history. 1, 2
The core hormonal panel should include:
- FSH and LH levels to differentiate between primary ovarian insufficiency (elevated FSH >40 mIU/mL), polycystic ovary syndrome (LH/FSH ratio >2), and hypothalamic causes (low-normal levels) 1, 2
- TSH to identify thyroid dysfunction as a reversible cause 1
- Prolactin to detect hyperprolactinemia (>20 μg/L), which may indicate pituitary adenoma or medication effects 1, 3
Understanding Post-Pill Amenorrhea
Most cases of amenorrhea after stopping birth control represent unmasking of pre-existing menstrual irregularities rather than a contraceptive-induced problem. 4 In one study, 63% of women with post-pill amenorrhea had irregular cycles before starting contraception 4. The pill essentially masked underlying ovulatory dysfunction, most commonly PCOS or hypothalamic amenorrhea 5, 2.
True post-pill amenorrhea (contraceptive-induced) is rare—only 2.5% of women have amenorrhea exceeding 3 months after stopping, and less than 0.5% exceed 6 months 4. This means your patient likely has an underlying condition requiring identification.
Interpreting Laboratory Results
If FSH is elevated (>40 mIU/mL on two occasions 4 weeks apart), this confirms primary ovarian insufficiency and requires karyotype testing if age <40 years. 1 These patients maintain unpredictable ovarian function and should not be presumed infertile 2.
If LH/FSH ratio >2 with normal/elevated estradiol, suspect PCOS. 1 These patients require screening for glucose intolerance and dyslipidemia as they are at risk for metabolic syndrome 2.
If FSH and LH are low-normal with low estradiol, this suggests hypothalamic amenorrhea. 1 Document weight changes, eating patterns, exercise habits, and calculate BMI 1. These patients require evaluation for eating disorders and are at risk for decreased bone density 2.
If prolactin is elevated, obtain MRI of the pituitary to exclude adenoma. 3
Additional Evaluation Based on Clinical Context
- Assess endometrial thickness via transvaginal ultrasound: thin endometrium (<5 mm) suggests estrogen deficiency; thick endometrium (>8 mm) suggests chronic anovulation with unopposed estrogen 1
- Pelvic ultrasound is indicated when clinical features suggest ovarian pathology or to evaluate for polycystic ovarian morphology 1
- Progesterone challenge test (medroxyprogesterone 10 mg daily for 10 days) can differentiate PCOS (positive withdrawal bleed) from hypothalamic amenorrhea (negative), though ultrasound assessment of endometrial thickness is more reliable 1
Common Pitfalls to Avoid
Do not assume amenorrhea is benign or self-limited without excluding serious pathology. Five of 63 women (8%) with post-pill amenorrhea in one series had significant organic disease including pituitary tumor, premature ovarian failure, or severe diabetes 4.
Do not delay evaluation beyond 6 months. By definition, secondary amenorrhea is cessation of irregular menses for 6 months, and your patient has reached this threshold 1, 2.
Do not miss hyperprolactinemia. Even mild elevations warrant pituitary imaging, as prolactinomas are a treatable cause 3.
Management Based on Diagnosis
For patients desiring pregnancy: Clomiphene citrate 50 mg daily for 5 days is first-line for ovulation induction in PCOS and certain cases of secondary amenorrhea of undetermined etiology, including post-contraceptive amenorrhea 6, 3, 4. Twelve of 19 women (63%) with post-pill amenorrhea achieved pregnancy with clomiphene or gonadotropins 4.
For patients not desiring pregnancy: Management depends on estrogen status. If hypoestrogenic (low estradiol, thin endometrium), provide hormone replacement therapy to prevent osteoporosis and cardiovascular disease 5. If euestrogenic (PCOS pattern), provide cyclic progestogen (medroxyprogesterone 10 mg for 10-14 days every 1-3 months) to prevent endometrial hyperplasia 5.
For hypothalamic amenorrhea: Address underlying causes (stress, excessive exercise, eating disorders) through counseling 5, 2. Provide estrogen replacement if hypoestrogenic to protect bone density 5.