You're doing everything right. You eat healthily, you don't smoke, and you might even be using a serum. Yet, your hair continues to thin. In such a case, it's natural to immediately think of hereditary hair loss. But there's another cause that's often overlooked, and that's your thyroid.
A thyroid that is underactive or overactive can significantly impact your hair. This doesn't apply to everyone with hair loss, far from it. But if you notice that your hair loss coincides with fatigue, a change in weight, or other vague symptoms, it's worth ruling this out before you look for other solutions.
What your thyroid has to do with your hair
Your thyroid produces the hormones T3 and T4. These control almost every process in your body, from your metabolism to your heart rate. Your hair follicles also need them. Each follicle goes through a cycle of growth, rest, and shedding, and thyroid hormones maintain that cycle.
If your thyroid is underactive or overactive, that cycle is disrupted. Follicles that would normally grow for years enter the resting phase prematurely. The result is that suddenly more hair is in that resting phase at the same time, leading to more hair loss than you're used to.
Underactive thyroid (hypothyroidism)
An underactive thyroid is more common in women, but men certainly experience it too. The symptoms usually build up slowly, so you might only take them seriously after months. You're tired, even after a good night's sleep. You gain weight without changes to your diet. Your hands and feet feel cold. Your skin becomes drier, you suffer more often from constipation, and sometimes there's that vague mental fog where concentrating just isn't easy. And on top of that: your hair is thinning.
The pattern of this hair loss differs from hereditary baldness. With an underactive thyroid, the hair thins evenly over the entire scalp, instead of developing a clear pattern such as a receding hairline or a bald crown. Some men also notice that the outer third of their eyebrows thins. That almost never happens with hereditary baldness.
An overactive thyroid can also be a cause
Less commonly known, but an overactive thyroid (hyperthyroidism) can also cause diffuse hair loss. This comes with other symptoms, such as unintended weight loss, heart palpitations, nervousness, excessive sweating, and an inability to tolerate heat. This can also be detected with a simple blood test.
How to distinguish it from hereditary hair loss
The two can seem similar, but there are clear differences. Hereditary hair loss (androgenetic alopecia) usually begins in a specific area, such as the temples or the crown, and slowly spreads over years. There is almost always a recognizable pattern, and family members on the father's or mother's side with baldness is also an indication.
Hair loss due to a thyroid problem occurs faster, often within a few months, is diffuse over the entire scalp, and almost never occurs in isolation. There are usually other symptoms, such as fatigue or a change in weight.
Good to know: the two are not mutually exclusive. You can be genetically predisposed to baldness and have a thyroid problem. In that case, an underactive thyroid simply accelerates the hair loss that your genes were already bringing about.
Which blood values to have tested
If you suspect your thyroid plays a role, a blood test is the only way to be sure. Ask your GP for TSH (thyroid-stimulating hormone) and free T4, and if the doctor deems it necessary, also free T3. An abnormal TSH is usually the first sign.
Because hair loss often has multiple causes simultaneously, it's smart to also have ferritin (your iron stores), vitamin D, and zinc measured in the same blood draw. A deficiency in any of these can also worsen hair loss independently of your thyroid, and this will save you a second appointment.
Your GP can request this blood test. There are also self-tests available without a referral, but always discuss the results with a doctor. Numbers without context say little.
Why this is so often missed
The symptoms appear gradually. You don't become tired in one week, and your hair doesn't fall out in one week. It creeps up over months, and because each symptom on its own seems explainable (stress at work, bad sleep, aging), you don't quickly put the pieces of the puzzle together.
GPs also don't immediately think of the thyroid in a thirty-year-old man with hair loss, and that's understandable: hereditary baldness is by far the most common cause in men. If you feel that there's more at play than just your hair, it's not an unreasonable request to ask for a blood test anyway. A GP can arrange that with a few vials of blood, and the result will at least give you clarity.
Also check if thyroid problems run in your family. Thyroid disorders often have a hereditary component, just like baldness, by the way. If a parent, brother, or sister has a thyroid problem, that's an additional reason to have yourself checked too.
What happens when your thyroid is treated
If your thyroid indeed turns out to be the cause, the treatment is usually simple: medication that normalizes your thyroid levels, for example, levothyroxine for an underactive thyroid. Once your levels are stable, the hair cycle will recover on its own.
Don't expect a quick turnaround. Hair grows slowly, and the follicles that were already in the resting phase need time to restart. Most men only notice improvement after a few months, and full recovery can take up to a year. This is frustrating if you want to see results quickly, but that's how a hair cycle works.
And if your blood values are good
If the blood test shows that your thyroid is working fine, then the cause of your hair loss is likely still genetic. In that case, it's more useful to look at what does influence hereditary hair loss, such as the sensitivity of your follicles to DHT.
For men whose blood values are in order and whose hair loss follows the pattern of hereditary baldness, a serum with active ingredients like our Growth Serum can be a logical next step. Not as a replacement for a blood test, but as an approach to hair loss that remains after you've ruled out other causes.
In short
Hair loss is not always genetic. A thyroid problem is one of the few causes that you can rule out or confirm with a simple blood test, and which is also easily treatable. If, in addition to hair loss, you also notice fatigue, weight changes, or other vague symptoms, consult your GP for a blood test before looking for a solution for your hair.
Frequently Asked Questions
Can you have a thyroid problem without blood tests immediately showing it?
Yes, with a mild or incipient abnormality, values may still fall within the normal reference range, even though symptoms are already present. In cases of persistent doubt, a doctor may choose to retest after some time.
Is there a difference in pattern between Hashimoto's and Graves' disease?
Yes, Hashimoto's usually leads to an underactive thyroid with associated diffuse hair loss, while Graves' disease causes an overactive thyroid with a slightly different set of symptoms, such as more nervousness and weight loss.
Can you get a temporary thyroid problem after pregnancy?
Yes, after pregnancy, a temporary thyroid inflammation known as postpartum thyroiditis can occur, which may be accompanied by hair loss. This usually resolves on its own, although it remains a permanent concern for some.
How long does it take for thyroid medication to be correctly adjusted?
Adjusting the correct dosage often takes several weeks to months, during which blood values are periodically checked and the dose is adjusted as needed.
Can you use a serum while waiting for the correct dosage?
Yes, you can. A serum works locally on the hair follicle and has no known interaction with thyroid medication, so you can use it while waiting for a stable adjustment.
Is there a link between iodine intake and thyroid problems with hair loss?
Yes, both a deficiency and an excess of iodine can disrupt thyroid function, which can then contribute to hair loss. In the Netherlands, severe iodine deficiency is rare, but it remains a factor to consider.
Can you reliably measure your TSH at home with a self-test?
Self-tests can provide an indication, but their reliability and interpretation are less consistent than a test performed by an accredited laboratory. Always discuss the results with a doctor.
Does stress affect thyroid function in a way that causes hair loss?
There is no strong evidence that stress directly disrupts thyroid function in a way that specifically leads to hair loss, although prolonged stress can also independently cause hair loss through telogen effluvium.
Can you develop a thyroid disorder at any age?
Yes, thyroid disorders can occur at any age, although some forms are more common during certain life stages, such as around pregnancy.
Is there a difference in recovery time between an underactive and an overactive thyroid?
In both forms, hair cycle recovery typically takes several months to a year after thyroid levels become stable, with no strongly demonstrated difference in recovery time.
