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Yes, a thyroid gland that works too slowly or too quickly can cause hair loss. This almost always concerns diffuse hair loss: your hair becomes thinner all over your head, not in individual bald spots[4]. This mainly happens with a serious or long-standing thyroid disorder, and you often only notice it a few months after the thyroid gland has become disrupted[4]. The good news: If the thyroid is treated properly, hair usually grows back. Count on several months and sometimes the recovery is not complete[4]. The first step is therefore always the doctor and a blood test, not a hair loss remedy. In this blog you can read which 5 signals indicate that your thyroid gland is involved, how recovery proceeds and when minoxidil is or is not an option afterwards.
In this article
- Can your thyroid cause hair loss?
- Which 5 signals indicate your thyroid gland?
- How does it differ from hereditary hair loss and alopecia areata?
- How long does it take for your hair to grow back?
- Can thyroid medication cause hair loss?
- Does minoxidil help with thyroid hair loss?
- Frequently asked questions
- Sources
Can your thyroid cause hair loss cause?
Yes. Thyroid hormone regulates the pace of many processes in your body, including the growth of your hair. Both an underactive thyroid gland (hypothyroidism) and an overactive thyroid gland (hyperthyroidism) can cause more hairs to enter the resting phase at the same time and fall out[4]. Doctors also mention an underactive thyroid gland as one of the known causes of telogen effluvium, the form of hair loss in which many hairs stop growing at the same time.[3].
Thyroid problems are not rare. It is estimated that 1.4% of the population has an underactive thyroid gland and 1.1% has an overactive thyroid gland. It is clearly more common in women than in men[1][2].
| Characteristic | Underactive thyroid gland | Overactive thyroid |
|---|---|---|
| How often (total) | About 1.4% of the population[1] | About 1.1% of the population[2] |
| Women and men | 2.2% of women, 0.6% of men | 1.7% of women, 0.5% of men |
| Hair and skin | Dry, rough or cold skin, rougher hair and hair loss | Warm, moist skin; diffuse hair loss is possible[4] |
| Other complaints | Tired, easily cold, gaining weight, constipation, slow heart rate | Heart palpitations, sweating, shaking hands, losing weight despite appetite |
| Examination | Blood test TSH and T4 | First TSH, then like this need free T4 and T3 |
Which 5 signals indicate your thyroid gland?
You cannot tell from your hair alone whether the thyroid gland is the cause. These signals make it more likely:
- Your hair is thinning everywhere. Thyroid hair loss is diffuse: your parting becomes wider and your ponytail becomes thinner, without loose bald spots[4].
- Your hair feels different. With a slow thyroid, the hair often becomes rougher and the skin drier[1].
- You also have other complaints. Think of tiredness, feeling cold quickly and gaining weight with a slow thyroid, or palpitations, sweating, shaking and losing weight with a fast[1][2].
- It started a few months after other complaints. Hair loss due to the thyroid only becomes visible a few months after the disorder started, because the hair cycle is slow[4].
- You clearly lose more than 100 hairs per day. More than 100 hairs per day is considered more than normal[3]. Also read how many hairs you lose per day and when it is too much.
Do you recognize this? Go to the doctor. A simple blood test (TSH, and if necessary T4) quickly shows whether your thyroid is working properly[1][2]. Other causes of diffuse hair loss are often examined, such as iron deficiency[4]. You can read more about this in our blog about hair loss due to iron deficiency.
Do you take biotin or a hair supplement with biotin? Tell your doctor: biotin can interfere with thyroid test results. It is often advised to stop taking it a few days before the blood test.[4].
How does it differ from hereditary hair loss and alopecia areata?
Hair loss can have several causes, sometimes at the same time. The pattern gives your doctor a first clue:
| Shape | Pattern | Course | First step |
|---|---|---|---|
| Through the thyroid | Diffuse, over the entire head | Usually recovers after treatment, in a few months | GP and blood test |
| Alopecia areata | Suddenly developing, often round bald spots | Often grows back on its own, can come back | GP (do not use minoxidil on your own) |
| Hereditary hair loss | Men: inlets and crown. Women: thinner around the parting | Gradually, continues without treatment | Minoxidil is a treatment with proven effect[3] |
Alopecia areata is an autoimmune condition that is more common in people with an autoimmune thyroid disease[4]. You then suddenly see bald spots without flakes or redness[3]. This is a different problem than diffuse thyroid hair loss and should always be discussed with your doctor.
How long does it take before your hair comes back?
Hair responds slowly to changes in your body. With telogen effluvium, hair usually falls out 2 to 4 months after the cause[3]. Once your thyroid is properly adjusted, it will take several months for your hair to grow back[4]. This is what a global gradient looks like:
The thyroid gland works too slowly or too quickly. You often first notice other complaints, such as tiredness or heart palpitations.
The hair loss becomes visible: more hair in the brush and the shower, the hair becomes thinner everywhere[4].
The doctor makes the diagnosis with a blood test and starts treatment if necessary. Setting the correct dose may take some time.
The hair usually grows back. The new hair may be slightly different in structure or color and the recovery is sometimes not complete[4].
Can thyroid medication cause hair loss?
This is a frequently asked question, because some people lose more hair just after starting their treatment. According to the British Thyroid Foundation, this is usually due to the thyroid disorder in the previous months, and not to the drug itself[4]. Medicines for an overactive thyroid (carbimazole and propylthiouracil) can in rare cases cause diffuse hair loss, but even then it is difficult to say what the cause is.[4].
Important: never stop taking your thyroid medication on your own because your hair is falling out. That can actually worsen hair loss[4]. If you are in doubt, discuss it with your doctor or pharmacist.
Does minoxidil help with hair loss due to the thyroid gland?
Minoxidil does not solve a thyroid problem. It is intended for hereditary hair loss, and there it has a proven effect in men and women[3]. The leaflet also clearly states that you should not use minoxidil if the cause of your hair loss is unknown, or in case of sudden or irregular hair loss[5]. If you suspect thyroid hair loss, do not start with minoxidil, but with your doctor.
When can minoxidil be an option? If your thyroid is properly adjusted, you are several months further and your hair still remains thin in the places that correspond to hereditary hair loss. Hair loss can have several causes at the same time, and a doctor can assess whether hereditary predisposition also plays a role. First discuss the use of minoxidil with your doctor or pharmacist.
Take into account the usual warnings: do not use under the age of 18, during pregnancy or breastfeeding, and not if there are indications of cardiovascular disease or heart rhythm disorders[5]. Because an overactive thyroid gland can itself cause palpitations and arrhythmias[2], consultation with your doctor is extra important here. Always read the package leaflet.
Foam for hereditary thinning hair in women, if the cause is known and your doctor agrees.
Lotion with the lower concentration most commonly used in women.
For men with hereditary hair loss at the crown, if the thyroid gland has been excluded or is properly controlled.
Frequently asked questions
Does hair grow back after thyroid hair loss?
Usually yes, if the thyroid gland is properly treated. It takes several months and the recovery is sometimes not complete. The new hair may feel slightly different or differ in color.
Can an overactive thyroid also cause hair loss?
Yes. Both an underactive and overactive thyroid gland can cause diffuse hair loss, especially if the disorder is severe or has persisted for a long time.
Should I stop taking levothyroxine if my hair is falling out?
No, never stop yourself. Hair loss after the start of treatment is usually due to the previous thyroid disorder. Stopping can make hair loss worse. Always consult with your doctor.
Can I use minoxidil if I have a thyroid disorder?
Not if the cause of your hair loss is still unknown. If your thyroid is properly adjusted and the hair remains thin in a pattern consistent with hereditary hair loss, discuss minoxidil with your doctor or pharmacist and read the package leaflet.
Which blood test shows whether my thyroid is the cause?
The doctor usually first has the TSH determined, supplemented with T4 if necessary. Other causes of diffuse hair loss are often also examined, such as iron deficiency.
Thyroid gland in order, hair still thin?
View minoxidil for hereditary hair loss and choose the form and strength that suits you, after consultation with your doctor.
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This article is general information and does not replace medical advice. Always read the package leaflet and, if in doubt, consult your doctor or pharmacist. Prices are as of November 2026.
Sources
- Health and Science (Cebam), Hypothyroidism (underactive thyroid)
- Health and Science (Cebam), Hyperthyroidism (underactive thyroid)
- Health and Science (Cebam), Hair loss
- British Thyroid Foundation, Hair loss and thyroid disorders (English)
- Medicine Evaluation Board, Medicines Information Bank, Package leaflet Minoxidil Bipharma 50 mg/g foam for cutaneous use
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