When periods stop, the two worries that usually come to mind first are: is it pregnancy, or is it a serious illness. In the clinic, in most cases it is neither, but amenorrhea is not a symptom to simply leave and watch; it is a signal whose cause must be sorted out step by step. Amenorrhea is a relatively common symptom in women of reproductive age, and for normal menstruation to occur, the axis running from the hypothalamus to the pituitary, the ovaries, and the uterus must all be working properly. In this article, rather than what the cause of amenorrhea is explained to be, I have organized the diagnostic process: what tests an obstetrician-gynecologist actually performs, and in what order, to narrow down the cause.
Before testing, we first align on the definition
Before testing for amenorrhea, we first confirm whether the current state is really amenorrhea that needs testing. Medically, amenorrhea is defined by several criteria. The absence of menarche by age 13 without secondary sexual characteristics, or the absence of menarche by age 15 with secondary sexual characteristics present, is regarded as primary amenorrhea. In someone who used to menstruate, the absence of menstruation for more than three times the previous cycle, or for 6 months or more, is classified as secondary amenorrhea.
This distinction matters because the direction of testing changes. Primary amenorrhea requires first examining problems in the formation of anatomical structures such as the uterus or vagina, while secondary amenorrhea traces where in the hormonal axis the stoppage occurred. This is a different matter from being a month or two late, so if you meet the above criteria, it is better not to delay testing and to come in. If you wonder whether the change of periods becoming sparse is the start of menopause, you may also refer to the article examining whether the absence of periods always means menopause.
We rule out pregnancy first
The first step in evaluating amenorrhea is, almost without exception, confirming whether there is a pregnancy. The American Society for Reproductive Medicine (ASRM)'s 2024 guideline on the evaluation of amenorrhea also recommends ruling out pregnancy first, before other tests. This is because the most common cause of periods suddenly stopping in women of reproductive age is pregnancy, and even if you think pregnancy is not possible, the principle is to confirm it with a test.
A pregnancy test is a simple test that checks the hCG hormone in urine or blood. In the clinic, it is not rare that at this stage the cause is settled and no further testing is needed. Once pregnancy is ruled out, we move on in earnest to hormone and imaging tests. If pregnancy and contraception themselves are a concern, you can separately get a consultation about situations requiring confirmation of pregnancy.
A negative pregnancy test does not mean testing is over; rather, that is where the real process of finding the cause begins.
Hormone tests trace where the stoppage occurred
Once pregnancy is ruled out, blood hormone tests trace where in the hypothalamus-pituitary-ovary axis the signal was cut off. The ASRM 2024 guideline and the American Academy of Family Physicians (AAFP) practice guideline advise measuring thyroid-stimulating hormone (TSH), prolactin, follicle-stimulating hormone (FSH), and estradiol (E2) as basic items in the initial evaluation of amenorrhea. Each value points to a different cause.
| Test item | Mainly examines | Implication if abnormal |
|---|---|---|
| TSH | Thyroid function | Menstrual changes due to thyroid dysfunction |
| Prolactin | Pituitary | Hyperprolactinemia, possible pituitary lesion |
| FSH | Ovarian function | Decline in ovarian function or pattern of early menopause |
| Estradiol | Estrogen status | Whether there is a low-estrogen state |
These four combined can sort out a considerable portion of the common causes of amenorrhea. For example, if FSH is high and estradiol is low, an ovarian problem is suspected; if prolactin is high, a pituitary cause is suspected. If polycystic ovary syndrome is clinically suspected, items related to male hormones may be added; if you are curious about this part, the article that explains polycystic ovary syndrome as a single keyword covers it in more detail.
Pelvic ultrasound is performed in almost all cases
Along with hormone tests, pelvic ultrasound is, in practice, a test included as a basic part of the evaluation of amenorrhea. With ultrasound, we first confirm whether the ovaries, uterus, and cervix are properly present. In primary amenorrhea, there may be a problem with the formation of the uterus or vagina itself, so the ASRM guideline also recommends pelvic ultrasound to check for structural abnormalities.
Ultrasound does not simply check whether organs are present. Measuring the thickness of the uterine lining and looking at it together with blood estrogen levels and the progestin withdrawal-bleeding response helps gauge whether ovulation is occurring. In an anovulatory state, endometrial hyperplasia is sometimes present, and pelvic ultrasound is always performed so as not to miss this. The following are the items mainly checked on pelvic ultrasound.
- The presence and shape of the ovaries, uterus, and cervix
- The thickness of the uterine lining
- The shape of the ovaries and the follicular pattern
- Whether there are accompanying findings such as endometrial hyperplasia
If a change of periods becoming irregular is bothering you, I recommend confirming a situation of irregular menstrual cycle together during a visit. If you are curious about the schedule or preparation for tests, you may ask in advance through an inquiry consultation on amenorrhea testing.
Imaging and hysterosalpingography are added when necessary
Not all patients with amenorrhea undergo imaging tests or hysterosalpingography. These tests are added selectively when a specific cause is suspected at an earlier stage. If a Müllerian anomaly is found in primary amenorrhea, tests such as pelvic CT or MRI, or intravenous pyelography, may be needed to check for accompanying genitourinary abnormalities.
Hysterosalpingography is a method of inserting a contrast agent to observe the inside of the fallopian tubes and the uterine cavity. It is used to check for uterine anomalies or intrauterine disease, and to see whether there is tubal occlusion or hydrosalpinx. It is performed especially when the condition of the fallopian tubes needs to be assessed in someone planning a pregnancy. It is a test that carries greater significance in situations where, beyond amenorrhea itself, an infertility evaluation is also needed. The following are representative situations in which additional imaging tests are considered.
| Situation | Test considered |
|---|---|
| Suspected Müllerian anomaly or genitourinary abnormality | Pelvic CT, MRI, intravenous pyelography |
| Suspected intrauterine disease or tubal abnormality | Hysterosalpingography |
| Persistently elevated prolactin | Pituitary MRI |
Brain imaging is done when hormone results point to it
Brain CT or MRI is not a test taken from the start in amenorrhea, but one performed when hormone results suggest a central nervous system cause. It is performed to distinguish lesions such as a pituitary adenoma or tumor when a low-hormone state that cannot be explained by stress or nutritional status persists, or when a high-prolactin state continues.
According to the AAFP guideline, when prolactin is persistently elevated, pituitary imaging is recommended, and in that case an MRI focusing intensively on the hypothalamus-pituitary region rather than the whole brain provides higher resolution. For reference, when amenorrhea appears due to Müllerian agenesis, accompanying anomalies of the genitourinary system such as the kidneys or ureters, and in some cases skeletal anomalies such as the spine, are also found together, so imaging tests also serve to check for accompanying abnormalities.
Knowing the order of tests makes the heart much more at ease
Amenorrhea testing is not done by cramming all tests in at once; it is a process of narrowing down step by step, starting with ruling out pregnancy and moving to hormones, ultrasound, and, when necessary, imaging tests. To summarize, it is a flow that begins with a pregnancy test, sorts out common causes with four hormones and pelvic ultrasound, and selectively adds hysterosalpingography or brain MRI depending on the direction the results point to.
Most amenorrhea stems from a simple cause, and if you do not leave it unaddressed and come in, the cause can be found and treated to fit your individual characteristics. If you are worried about early menopause, the article dealing with the prevention and treatment of premature menopause may help, and if you are considering regular women's health check-ups, lifecycle screening may help. If you have had no period for 6 months or more, or hesitate about testing, please first use a consultation on whether amenorrhea testing is needed.
Written by: Lee Dong-hee Director · Obstetrics and Gynecology Specialist · See physician profile
First published January 2, 2024 · Last reviewed May 30, 2026
References: American Society for Reproductive Medicine, Current Evaluation of Amenorrhea Committee Opinion (2024), American Academy of Family Physicians, Amenorrhea Evaluation and Treatment (2006)
This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.