When periods that were once regular stop, the question is not whether to investigate but where to start. Klein and Poth (Endocr Pract 2013) outlined the standard approach, which has held up in subsequent guidelines: rule out pregnancy first, then work through the most common causes in a deliberate sequence.
This post covers the definition, the prioritized workup, the major diagnostic categories, and when to escalate to a specialist.
What secondary amenorrhea is
- Primary amenorrhea: never had a period (by age 15 if breast development has begun, or by age 13 with no breast development). Different workup, not the focus here.
- Secondary amenorrhea: no period for 3 or more months in someone with previously regular cycles, OR 6 or more months in someone with previously irregular cycles.
Secondary is more common than primary by orders of magnitude.
Step 1: pregnancy test, every time
The first step, even when you are sure pregnancy is impossible, is a urine or serum hCG. Many clinicians have stories of patients adamant about no possibility of pregnancy whose first test was positive.
For test timing logic, see pregnancy test timing.
If pregnancy is confirmed, the workup pivots to prenatal care.
Step 2: history and exam
What you bring to the visit narrows the differential dramatically:
- Cycle history. When was the last normal period? Were cycles regular before they stopped? How were they regulated (oral contraceptives, nothing)?
- Recent stressors. Work, relationships, illness, surgery, weight changes (loss or gain), exercise volume.
- Eating patterns. Restrictive eating, binge eating, current intake levels.
- Symptoms. Hot flashes, vaginal dryness, hair changes, acne, galactorrhea (milky discharge), vision changes, headaches, mood changes.
- Medications. Hormonal contraceptives recently stopped, antipsychotics (raise prolactin), some antidepressants, opioids, certain steroids.
- Pregnancy history. Recent pregnancy or breastfeeding.
A focused exam looks for thyroid abnormalities, galactorrhea, hirsutism, acne, signs of hyperandrogenism, signs of hypothalamic amenorrhea (low body weight, low body fat).
Step 3: initial labs
Standard first-pass labs after pregnancy is excluded:
- TSH. Thyroid disease is a common, easily treated cause. See thyroid and menstrual cycles.
- Prolactin. Hyperprolactinemia commonly causes amenorrhea via GnRH suppression. Causes include pituitary microadenoma, certain medications, hypothyroidism, stress.
- FSH and estradiol. Help distinguish ovarian failure (high FSH, low estradiol) from hypothalamic suppression (low FSH, low estradiol) from normal-cycling but anovulatory states.
- Total and free testosterone, DHEAS if hyperandrogenism is suspected.
- LH can be useful in PCOS evaluation.
- AMH. Sometimes added to clarify ovarian reserve. See AMH and ovarian reserve.
The pattern of these labs steers diagnosis.
The major diagnostic categories
Pregnancy
Already covered. Confirm or rule out.
PCOS
The most common cause of secondary amenorrhea outside of pregnancy. Diagnosis follows the Rotterdam criteria (2 of 3): oligo-/anovulation, hyperandrogenism (clinical or biochemical), or polycystic ovaries on ultrasound. See PCOS Rotterdam criteria explained.
Lab pattern: normal or mildly elevated LH, normal FSH, elevated free testosterone, normal estradiol, sometimes elevated DHEAS.
Treatment: lifestyle, combined hormonal contraceptives, metformin, ovulation induction depending on goals. See PCOS and insulin resistance.
Hypothalamic amenorrhea (HA)
Reduced GnRH pulsatility from inadequate energy availability — often a combination of under-eating, over-exercising, or chronic stress. Classic in athletes, dancers, people with restrictive eating, or those navigating major life stress.
Lab pattern: low or low-normal LH and FSH, low estradiol, normal prolactin, normal TSH.
Treatment: restoring energy availability — eating more, training less, addressing stress and disordered eating. See hypothalamic amenorrhea explained and stress and missed periods.
Hyperprolactinemia
Elevated prolactin suppresses GnRH and stops ovulation. Causes:
- Prolactinoma. Pituitary tumor, usually benign. Microadenomas are common.
- Medications. Many antipsychotics, some antidepressants, metoclopramide, opioids.
- Hypothyroidism. TRH stimulates prolactin.
- Stress, recent breast stimulation, or recent breastfeeding.
- Macroprolactin (a non-functional form) can cause spuriously high readings.
If prolactin is elevated, repeat the test fasting and avoiding breast stimulation. Persistent elevations warrant imaging (typically pituitary MRI) to evaluate for adenoma.
Treatment: dopamine agonists (cabergoline, bromocriptine) for prolactinomas. Treat underlying cause for medication- or thyroid-driven hyperprolactinemia.
Thyroid disease
Both hypo- and hyperthyroidism can cause amenorrhea. TSH alone catches most cases. Treatment typically restores cycles within 1 to 3 months of stable, in-range labs.
Premature ovarian insufficiency (POI)
POI is loss of ovarian function before age 40. Diagnosis: amenorrhea or oligomenorrhea with FSH in the menopausal range (above 25 to 30 mIU/L) on two occasions at least 4 weeks apart, with low estradiol.
Causes: idiopathic (most common), genetic (Turner syndrome, fragile X premutation), autoimmune, iatrogenic (chemotherapy, radiation, surgery).
POI is often missed for months because clinicians do not check FSH early. Symptoms (hot flashes, vaginal dryness, mood changes, sleep disruption) overlap with normal life stress.
Management includes hormone therapy until typical age of menopause, fertility counseling (donor-egg IVF is the most reliable path to pregnancy), and screening for related autoimmune conditions. Bone density and cardiovascular risk both rise with early estrogen loss.
Asherman syndrome
Intrauterine scarring after instrumentation (D&C, especially after retained pregnancy tissue or postpartum hemorrhage). Suggested by amenorrhea after a known uterine procedure with no endometrial response despite hormonal stimulation. Diagnosis is hysteroscopic.
Post-pill amenorrhea
After stopping hormonal contraception, most people resume cycles within 3 months. A small fraction takes 6 to 12 months. If amenorrhea persists past 6 months post-pill, it is generally considered to reveal an underlying cause (PCOS, HA, thyroid, prolactin) rather than be caused by the pill itself.
Postpartum / breastfeeding amenorrhea
Lactational amenorrhea is normal. Most people resume cycles within 6 to 12 months postpartum depending on breastfeeding intensity. See postpartum period return.
A simplified algorithm
- Pregnancy test. Positive → prenatal care. Negative → continue.
- TSH, prolactin, FSH, estradiol.
- TSH abnormal: treat thyroid, recheck in 6 to 12 weeks.
- Prolactin elevated: confirm, evaluate causes, image if persistently elevated.
- FSH high (above 25 to 30): likely POI, repeat in 4 weeks, plan accordingly.
- FSH and LH low or low-normal, estradiol low: likely hypothalamic amenorrhea, evaluate energy availability and stress.
- Hyperandrogenism present: evaluate for PCOS using Rotterdam criteria.
- All labs normal but no withdrawal bleed after progestin challenge: consider Asherman syndrome or persistent hypothalamic suppression.
When to refer
Refer to reproductive endocrinology for:
- Suspected POI.
- Hyperprolactinemia with imaging needs.
- PCOS not responding to standard management.
- HA with disordered eating requiring multidisciplinary care.
- Asherman syndrome (referred to gynecologic surgery).
- Anyone trying to conceive whose workup has not yielded a clear plan.
What to track
Even partial cycle data is useful. The Period Calculator lets you log when periods stopped, any spotting, and any return of cycles. The Ovulation Calculator is helpful when cycles resume to confirm ovulation patterns. See also anovulation and irregular cycles for the broader picture.
Questions worth asking
- Have we tested pregnancy, TSH, prolactin, FSH, and estradiol?
- Has my clinician asked about energy intake and exercise volume?
- Has my clinician asked about disordered eating?
- Should I see a reproductive endocrinologist?
- If I am not actively trying to conceive, what is the bone-health and long-term plan?
The bottom line
Periods stopping is a real symptom that deserves a real workup. The sequence — pregnancy first, then TSH, prolactin, FSH and estradiol, then hyperandrogen evaluation if relevant — catches the large majority of causes. Most are treatable. The cause matters because the answer to “will my periods return” depends on it. If your evaluation has stalled, ask for the next step.