A dysfunctional thyroid can significantly affect your metabolism, nervous system, and heart function [1]. But it is a lesser-known fact that thyroid disorders can cause hair loss as well. Studies show that hair shedding is a symptom in approximately 50% of people who experience hyperthyroidism and 33% of those with hypothyroidism [2].
That is because hormones secreted by the thyroid gland play an important role in regulating your hair growth cycle, stimulating strand production and preventing oxidative stress [2][3]. If they become imbalanced, they can lead to diffuse hair thinning. And autoimmune thyroid conditions have been associated with an increased risk of developing alopecia areata.
The good news is that most common thyroid conditions can be managed with medication. After stabilisation is achieved, your hair loss may resolve as well [3], although strand regrowth is not always achieved. If you have been treating your thyroid disorder for several months and your hair is still falling out, it is recommended to see a trichologist. They will perform the necessary blood tests for hair loss and offer you an accurate diagnosis and treatment.
This article will tell you everything you need to know about:
The thyroid is an endocrine (hormone-producing) gland located at the lower front of your neck. Its role is to produce specific hormones, called thyroxine (T4) and triiodothyronine (T3). These hormones are extremely important to the functioning of your body, as they are involved in the function and metabolism of most types of cells. Some of the processes they support are [1][4]:
There are two main kinds of thyroid disorders: the ones that make your thyroid hyperactive (producing too many hormones) and those that make it underactive (producing too few hormones). The first case is called hyperthyroidism, while the second is known as hypothyroidism.
In most cases, these conditions are caused by autoimmune thyroid disorders, such as Graves Disease (also known as Basedow Disease) [5], or Hashimoto thyroiditis, where your body’s own immune system attacks your thyroid [6][7][8]. But they can also be caused by thyroid nodules (lumps), excessive levels of iodine, treatment with certain kinds of medications (e.g. lithium, interferons, amiodarone), thyroid inflammation, hormonal changes caused by pregnancy and childbirth or, rarely, thyroid cancer [9][10].
Here are the main symptoms to look out for in thyroid disorders:
Thyroid hormones play an important role in hair follicle growth and health. If their level drops or increases significantly, it can disrupt your hair growth cycle and produce alterations in strand strength and texture. That is likely why studies have found thyroid disorders in many alopecia cases [2][11][12].
While this happens more often with prolonged hypothyroidism, it can also occur in patients with clinical-level hyperthyroidism. Here are the mechanisms through which thyroid dysfunction can make your hair fall out [2]:
In a healthy person, hair undergoes a natural cycle of growth, resting and shedding. At any given time, approximately 86% of your hairs are in the anagen (growth) phase, 1% are in the catagen (transition) phase and 13% are in the telogen (resting and shedding) phase, with 100-150 strands normally falling out each day [2]. Each of your hair follicles goes through this cycle, which lasts approximately 3-7 years to complete.
Since not all of your strands are in the same phase at the same time, the shedding hairs do not lead to visible thinning, as new ones are constantly growing to replace them.
However, if this cycle is disrupted, excessive hair loss can indeed occur. Both hypothyroidism (in most cases) and hyperthyroidism can cause hair loss by modifying the duration of the growth and shedding phases. This can lead to a type of alopecia called telogen effluvium, which causes diffuse hair loss [2][12].
Telogen effluvium occurs when the growth phase of the hair follicles is shortened and the shedding one extended, so a greater proportion of strands are falling out simultaneously.
Prolonged low levels of thyroid hormones can affect blood circulation, including to the capillaries in your scalp. Moreover, they can also decrease your metabolic activity [1]. Both these processes can lead to a lower amount of oxygen and nutrients reaching your hair follicles, slowing down your hair growth and decreasing strand strength and thickness.
Hypothyroidism can have a negative effect on the production of the natural oil (sebum) your scalp and hair need to stay hydrated. Thus, it can lead to dry, brittle, coarse and dull strands, which break off easily. On the other hand, hyperthyroidism can make your strands finer than normal, reducing their mechanical strength and increasing hair breakage [2]. So a thyroid condition may be the reason your hair feels thinner and more fragile.
Alopecia areata is an autoimmune type of hair loss where your white blood cells are attacking your hair follicles. It typically creates smooth, round bald patches on your scalp, in your eyebrows or beard. However, in certain cases, it can also present as diffuse hair loss.
While further research is needed to determine the exact nature of the relationship between alopecia areata and other autoimmune conditions, studies have shown an association between this kind of hair loss and autoimmune thyroid disorders, such as Hashimoto’s thyroiditis or Graves’ disease [12][2][13]. Diffuse alopecia areata has been found in up to 50% of patients with hyperthyroidism, while approximately 5% of patients with this condition experience hypothyroidism related to Hashimoto’s disorder [14][2].
It appears that there is a two-way relationship between these autoimmune disorders, as being diagnosed with either one increases the risk of also developing the other. So experiencing an autoimmune thyroid can make it more likely that you also develop alopecia areata.
Thyroid hormones play a role in the functioning of an enzyme called 5 alpha-reductase, which converts testosterone into a different androgen called dihydrotestosterone (DHT) [15]. When excessive amounts of this male hormone are produced, it binds to the androgen receptors in your hair follicle, preventing them from producing new hair. That is how androgenetic alopecia (male pattern baldness or female pattern baldness) is developed.
Moreover, thyroid dysfunctions can influence estrogen metabolism and availability, impeding its protective and hair-growth-stimulating functions on your hair follicles.
One study shows that 31.25% of women with female pattern baldness also experience hypothyroidism [2]. A different study, performed on both men and women with androgenetic alopecia revealed a 50% rate of thyroid dysfunctions in patients older than 40 [12].
While there are theories saying that thyroid disorders can trigger or worsen symptoms in people who are genetically predisposed to developing androgenetic alopecia, further research is needed to confirm this effect and to better understand its circumstances [12].
Finally, pregnant women are more predisposed to developing Graves’ disease, an autoimmune thyroid disorder. And the many hormonal changes in their bodies (including an increase in thyroid hormone production, to help with foetal growth and development) can mask its symptoms, making it more difficult to diagnose in a timely fashion. This is why a thyroid condition may cause hair loss during pregnancy [22].
Most commonly, people with thyroid-induced hair loss experience diffuse hair shedding all over their scalp, due to disruptions in their hair growth cycle [2][16]. Their hair may grow slower and depending on the type of thyroid disorder they have, it might be either coarser or finer than usual. In most cases, the strands are dry and brittle and break off easily, which often leads to hair breakage and split ends [3].
Moreover, studies have found a strong association between thyroid dysfunctions and premature greying, but also common scalp conditions, such as scalp psoriasis and seborrheic dermatitis [17].
While the relationship between alopecia areata and an autoimmune thyroid is still being investigated, studies reveal that conditions such as Graves’ Disease or Hashimoto thyroiditis increase the risk of developing this type of alopecia (although not necessarily by causing it) [13]. In this case, patients experience round patches of hair loss on their scalp, or in some cases, diffuse hair loss.
Finally, the hair on your head may not be the only one affected by thyroid disorders, you may also experience eyebrow hair loss [23], beard hair loss or, very rarely, shedding of all your head and/or body hair (e.g. alopecia totalis or alopecia universalis).
While hair loss is more common in men than in women, thyroid-induced hair loss is more frequently seen in the female population. That is because women are up to 500% more likely to experience thyroid dysfunctions that can lead to hair shedding than men [18]. Studies have revealed that hyperthyroidism is present in 1.5% of women and 0.5% of men, while hypothyroidism affects 3% of the male and 10.5% of the female population [18].
Thyroid disorders are also more likely to affect people as they advance in age (especially after the age of 60) [18], but also pregnant and postpartum women [7]. People who have congenital thyroid dysfunctions are, of course, at increased risk of developing hair shedding, depending of the severity of their condition. As are those with a family history of thyroid dysfunction, or people who experience certain predisposing illnesses, such as type 1 diabetes, Turner syndrome or an autoimmune disorder [20][13][21].
Moreover, research suggests that thyroid dysfunctions may play a role in triggering early onset androgenetic alopecia or worsening its symptoms in people who are already genetically predisposed to developing this condition (although further evidence is needed to understand the nature of their correlation) [2][17].
Some people can expect to see hair regrowth a few months after starting treatment to manage the thyroid condition which caused their hair shedding [3]. However, this regrowth may sometimes be incomplete and in some patients, it may not happen at all [14].
That is why early diagnosis is important in thyroid disorders, as it can not only help you get your condition under control faster and with a lower toll on your body, it can also help you limit the extent of your hair shedding early on.
Since hair loss caused by thyroid disorders represents a systemic type of alopecia, the best thing you can do is address the underlying cause. That means getting your condition under control with medication significantly increases your chances of achieving hair regrowth. However, this does not happen in all patients with thyroid dysfunctions even after successful treatment.
If after a few months of treatment, this doesn’t happen to you, it is important to see a trichologist. They will be able to diagnose your hair loss and may prescribe some of the following treatments to curb your hair loss and stimulate your follicles for hair growth:
While many people who experience a thyroid disorder also report hair shedding, booking a consultation with a trichologist is the best way to check if the two conditions are related in your case. The doctor will examine your hair and scalp thoroughly and may order blood tests to exclude other conditions that cause your hair to fall out, such as vitamin deficiencies that cause hair loss or medication-induced hair loss.
Sometimes, even a hair specialist will have difficulty determining the relationship between your hair shedding and thyroid dysfunction with certainty. That is because when it comes to conditions such as androgenetic alopecia or alopecia areata, there is currently insufficient research to shed light on this matter.
While both these types of alopecia are associated with higher rates of abnormal thyroid hormone levels, further evidence is needed regarding whether they are caused by this dysfunction or simply share common predisposing factors [2]. And telogen effluvium can be triggered by a variety of physically and psychologically stressful experiences.
However, what your trichologist can do is take all the evidence into account, alongside your hair and scalp particularities, your medical history and preferences and recommend the best hair loss treatment for women (or, by case, the most effective hair loss treatment for men) with your specific hair growth needs.
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