An underactive thyroid — known medically as hypothyroidism — is one of the most common underlying causes of hair loss and hair texture change that a trichologist encounters in clinic. It is also one of the most frequently missed, because thyroid symptoms develop gradually and are easy to attribute to other causes: stress, ageing, the change of seasons, or simply needing a better shampoo.
If your hair has become noticeably drier, more brittle, or straw-like, and you are experiencing other symptoms such as fatigue, weight gain or feeling cold all the time, your thyroid is worth investigating. At Fibre Trichology in Congleton, Cheshire, Mandy regularly works with clients whose hair loss has a thyroid cause — here is what you need to know.
The thyroid is a small butterfly-shaped gland in the neck that produces hormones regulating the body’s metabolic processes. When it is underactive, it produces insufficient levels of these hormones — primarily thyroxine (T4) and triiodothyronine (T3) — and the body’s systems slow down as a result.
Hypothyroidism is more common in women than men, and becomes increasingly common with age. It is strongly associated with autoimmune disease — the most common cause is Hashimoto’s thyroiditis, in which the immune system attacks the thyroid gland over time. It can also develop following thyroid surgery, radioactive iodine treatment, or certain medications.
Thyroid hormones play a direct role in regulating the hair growth cycle. When levels are insufficient, the cycle is disrupted — more follicles than usual shift into the resting (telogen) phase and stay there for longer, resulting in increased shedding and reduced regrowth. At the same time, the reduced metabolic activity affects the follicle’s ability to produce healthy, strong hair — which is why hypothyroidism affects not just how much hair you have, but how the hair itself looks and feels.
Hair loss associated with hypothyroidism tends to be diffuse — meaning it affects the scalp generally rather than producing isolated patches. This makes it easy to confuse with other types of diffuse hair loss, including telogen effluvium and female pattern hair loss, which is another reason why proper assessment matters.
The hair changes associated with hypothyroidism typically include:
These hair changes rarely occur in isolation. Other symptoms of hypothyroidism that commonly accompany the hair changes include persistent fatigue, unexplained weight gain, feeling cold even in warm environments, dry skin, low mood, difficulty concentrating, constipation and irregular periods.
If several of these sound familiar alongside the hair changes you have noticed, thyroid function is strongly worth investigating.
This is where many clients hit a frustrating obstacle. The standard NHS thyroid test measures TSH — thyroid stimulating hormone — alone. While TSH is a useful screening marker, it does not always tell the full story. TSH can sit within the reference range while Free T3 and Free T4 — the active thyroid hormones that directly affect the hair follicle — are low enough to be causing symptoms.
A full thyroid panel including TSH, Free T3 and Free T4 gives a much more complete picture. Thyroid antibodies — anti-TPO and anti-thyroglobulin — are also worth testing where autoimmune thyroid disease is suspected, as antibody levels can be elevated well before thyroid function tests move outside the reference range.
Our detailed guide to blood tests for hair loss covers what to ask for and how to interpret the results in the context of hair health — including why results that appear “normal” are not always optimal.
In many cases, yes — once thyroid hormone levels are adequately replaced through medication, the hair growth cycle can normalise and regrowth occurs over time. However, this is not always immediate and is not always complete.
Hair grows slowly — typically around one to two centimetres per month — so even once thyroid levels are optimised, rebuilding visible density takes months rather than weeks. Some clients find that hair regrowth is not as full as it was before the thyroid condition developed, particularly where the condition went undiagnosed for a long period.
This is one reason why early identification matters. The sooner thyroid dysfunction is identified and treated, the less damage accumulates to the hair follicles over time.
It is not uncommon for clients to find that even with their thyroid levels well managed on medication, their hair has not fully recovered. There are a few reasons this can happen:
A trichology consultation is particularly valuable in this situation. Mandy can assess the full picture — including the hair loss pattern, any other contributing factors, and the current state of the scalp and follicles — and recommend a targeted plan to support recovery beyond what thyroid medication alone achieves.
Alongside hair loss, the change in hair texture that hypothyroidism causes can be just as distressing. Hair that was once soft and manageable becoming dry, coarse and difficult to style is a common complaint — and one that conditioners and hair masks alone will not resolve if the underlying thyroid cause is not addressed.
For a broader overview of the medical conditions that can cause hair texture to change, our post on medical conditions that cause hair texture change covers the full range of causes in detail. And if your hair specifically feels dry and straw-like, our post on why hair feels like straw explains the causes and what can be done.
At Fibre Trichology, a trichology consultation for thyroid-related hair loss will involve a detailed assessment of the hair loss pattern, texture changes and timeline, alongside a review of your thyroid history, current medication and any other health factors that may be contributing.
Where appropriate, Mandy will advise on which blood tests are worth requesting — both thyroid-specific and broader nutritional markers — and help you interpret the results in the context of your hair health. A personalised treatment plan can then be put in place to support recovery alongside your thyroid treatment, which may include:
If you suspect your thyroid may be affecting your hair — or if you have a thyroid condition and your hair has not recovered as expected — Fibre Trichology in Congleton, Cheshire can help. Mandy is a registered member of the Association of Registered Trichologists with over 40 years of experience in hair and scalp health, and sees clients from across Cheshire and the North West.
Get in touch today to book your trichology consultation, or read more about why hair falls out to help you understand what might be contributing to your hair loss before your appointment.
Fibre Trichology, Mill Street Collective, 13 Mill Street, Congleton, CW12 1AB. Call 07780 600532 or email info@fibretrichology.co.uk.
Mandy Graham is a registered member of the Association of Registered Trichologists with over 40 years of experience in hair and scalp health.
