Thyroid problems vs perimenopause: how to tell them apart

Perimenopause and thyroid disease can look remarkably alike: both can bring fatigue, poor sleep, mood changes, weight change, hair changes and irregular periods, and both are common in women in their 40s and 50s. The practical way to tell them apart is a blood test, because TSH reliably detects an overactive or underactive thyroid while perimenopause has no confirming test. Check the thyroid first when symptoms overlap; if it is normal, perimenopause and other causes move up the list, and remember the two can occur together.

Symptoms side by side

Symptom	Perimenopause	Underactive thyroid	Overactive thyroid
Temperature	Hot flashes in waves, night sweats	Trouble tolerating cold	Sweating, feeling hot, trouble tolerating heat
Energy	Fatigue, often from broken sleep	Fatigue	Fatigue, or increased or decreased energy
Mood	Irritability, anxiety, low mood	Depression, low mood	Anxiety, nervousness, irritability
Sleep	Waking at night, often with sweats	Not on standard symptom lists	Trouble sleeping
Heart	Palpitations, often with hot flashes	Slow heart rate	Racing or irregular heartbeat
Weight	Gain is common in midlife	Weight gain	Weight loss despite a normal or bigger appetite
Periods	Irregular, skipped, heavier or lighter	Heavy or irregular	Lighter or less frequent
Bowels	No specific change	Constipation	Frequent bowel movements or diarrhea
Other	Vaginal dryness, pain with sex	Dry skin, dry or thinning hair, forgetfulness	Shaky hands, hair loss, neck fullness, eye pain or bulging

The most discriminating features are hot flashes that come in waves and vaginal dryness for perimenopause; feeling cold, constipation and a slow pulse for an underactive thyroid; and tremor, weight loss and a fast resting pulse for an overactive one. Our list of perimenopause symptoms covers the perimenopause column in more detail.

The catch is that most women have the overlapping symptoms, not the discriminating ones. The NIDDK notes that many hypothyroid symptoms, especially fatigue and weight gain, are common and do not necessarily mean a thyroid problem. A Colorado study of 25,862 people tested at a health fair found that hypothyroid symptoms were reported more often by people with an underactive thyroid, but any single symptom had low sensitivity: it missed many of the people who had thyroid disease. The authors concluded that people with several such symptoms warrant a blood test.

How common thyroid disease is

The US national survey NHANES III measured thyroid function in 17,353 people aged 12 and older. It found hypothyroidism in 4.6 percent, most of it mild (0.3 percent clinical, 4.3 percent subclinical), and hyperthyroidism in 1.3 percent. Thyroid peroxidase antibodies, a marker of the autoimmune thyroid disease that causes most hypothyroidism, were present in 11.3 percent, more often in women and more often with age. The authors noted that a large share of the population had laboratory evidence of thyroid disease without knowing it.

The NIDDK adds that women are much more likely than men to develop hypothyroidism and that it is more common after 60. The American Thyroid Association notes that Graves’ disease, the most common cause of an overactive thyroid, happens more often in younger women.

The tests that tell them apart

The American Thyroid Association calls TSH the best first test of thyroid function, because changes in TSH often appear before thyroid hormone levels become abnormal. A free T4 test is added when TSH is abnormal.

Result	What it usually means
Normal TSH	Thyroid disease is unlikely to explain your symptoms
High TSH, low free T4	Underactive thyroid (primary hypothyroidism)
High TSH, normal free T4	Mild, or subclinical, hypothyroidism
Low TSH, high T4 and/or T3	Overactive thyroid (hyperthyroidism)
Low TSH, normal T4 and T3	Subclinical hyperthyroidism; many people have no symptoms
Low TSH, low free T4	Possible pituitary problem

Antibody tests help identify the cause once thyroid disease is found: thyroid peroxidase and thyroglobulin antibodies for autoimmune thyroiditis, and TSH receptor antibodies for Graves’ disease. The ATA notes that T3 testing rarely helps in suspected hypothyroidism.

Perimenopause has no counterpart. FSH and estradiol swing widely from month to month, so a normal result does not rule it out and an abnormal one does not confirm it; see why hormone tests are often normal. Perimenopause is diagnosed from age, cycle changes and symptoms after other causes have been considered, which is exactly why the thyroid test comes first.

Two pitfalls that distort results

• Estrogen. Birth control pills, pregnancy and other estrogen sources raise the proteins that carry thyroid hormone, which pushes total T4 and T3 up. The ATA advises measuring TSH and free T4 instead, which typically stay normal. Tell the lab and your clinician about any hormones you take.
• Biotin. This popular hair and nail supplement can make several thyroid tests look abnormal when they are not. The ATA advises stopping biotin for 2 days before blood is drawn.

When it is both

Having one condition does not protect you from the other. Two points matter if you already take thyroid medication.

First, treated is not always well treated. In the Colorado study, 40 percent of people taking thyroid medication had an abnormal TSH. If symptoms persist, a TSH check is a sensible first step.

Second, a normal TSH on treatment with persistent fatigue, poor sleep or brain fog may point elsewhere, and perimenopause is one possibility worth considering. Starting or stopping estrogen can also change the levothyroxine dose you need; the ATA lists estrogen, along with calcium and iron supplements, among things that affect thyroid pills and advises a blood test 6 to 8 weeks after any dose change. Our guide to perimenopause with thyroid disease covers managing both.

Clues that call for a prompt check

• A resting heartbeat that is persistently fast, irregular or unusually slow; see heart palpitations
• Weight loss you cannot explain, especially with a good appetite
• Shaky hands, swelling or fullness in the neck, or eye pain or bulging
• High cholesterol, which the NIDDK says should prompt a hypothyroidism test
• Heavy periods with exhaustion

A practical sequence

1. Note your symptoms and your cycle for a few weeks.
2. Ask for a TSH, with free T4 if it is abnormal. Pause biotin for 2 days first, and mention any estrogen you take.
3. If the thyroid is abnormal, treat it and recheck before deciding what is left over.
4. If TSH is normal, perimenopause, sleep disruption, iron deficiency and mood disorders are the next explanations to explore.

Primary care can handle most of this. An endocrinologist is useful for an overactive thyroid, nodules, a dose that is hard to stabilize, or when both conditions are active at once.