Thyroid Disease
A: These changes can be signs and symptoms of thyroid disease. While thyroid issues are just one of several potential reasons for hair loss, they often cause distinct patterns. Overall thinning across your scalp, and changes such as dry, coarse, or brittle hair, and loss of eyebrow hair (particularly the outer third of the eyebrows) can occur with thyroid disease.
How Thyroid Hormones Affect Hair Growth
Hypothyroidism (an underactive thyroid) is one common cause, though hyperthyroidism (an overactive thyroid) can also cause widespread hair thinning. However, these symptoms are not unique to thyroid disease alone. Because hair loss has many overlapping causes, thyroid function is checked when your symptoms or medical history point to a potential thyroid issue.Think of your thyroid as the engine's regulator for many of your body's functions. If it is running too slowly, your metabolism decreases, causing your hair follicle cells to divide more slowly. This shift leaves you with dry, coarse, or thinning hair, and it frequently causes the outer third of your eyebrows to become noticeably thin.
You might also experience other common symptoms of an underactive thyroid, such as unexplained fatigue, feeling unusually cold, weight gain, low mood or depression, constipation, dry skin, weak muscles, or a raspy or hoarse voice. However, because these symptoms are non-specific and overlap with conditions like vitamin deficiencies or anemia, they do not by themselves prove that you have a thyroid disorder.
Testing, Treatment and Hair Regrowth
There is a simple, highly accurate blood test to check thyroid function. The primary screening test is Thyroid-Stimulating Hormone (TSH). If TSH levels are abnormal, your doctor will order extra follow-up tests. Routine annual thyroid testing is not necessary for everyone, but testing is appropriate when you have symptoms, risk factors, or are taking medications known to impact thyroid performance.If your hair loss is related to an underactive thyroid, treating the thyroid problem is the essential first step. For most people, hair loss stops and reverses once thyroid hormone levels return to a balanced state. However, because the hair growth cycle is long, noticeable regrowth often takes 3 to 6 months after starting treatment. You might even notice a brief period of increased hair shedding during your first few weeks on medication. This happens because new growing hairs are pushing the old hair follicles out.
The standard treatment for an underactive thyroid is synthetic thyroid hormone replacement, most commonly levothyroxine. Blood tests are repeated 6 to 8 weeks after starting treatment or after adjusting the dose, to make sure your dose is correct. Certain types of hypothyroidism (such as thyroiditis following pregnancy or temporary side effects from specific medications) are temporary, while others (especially autoimmune hypothyroidism) require lifelong treatment.
See a Doctor
If you recognize any of these symptoms in yourself, do not wait to have them evaluated. Thyroid problems often run in families, so be sure to tell your doctor if any relatives have hypothyroidism, autoimmune conditions, or general thyroid issues. Having a family member with thyroid disease increases your risk, though it does not mean you will get it too.Your doctor can evaluate your symptoms and order the appropriate blood tests. A dermatologist can also be helpful when hair loss is a primary concern. A dermatologist can help rule out co-occurring conditions like iron deficiency anemia, vitamin D deficiency, or androgenetic alopecia. A dermatologist specializing in hair disorders can perform a scalp examination to pinpoint all contributing factors.
This answer is intended for informational purposes only. For medical advice or a diagnosis, contact a doctor.
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See also:
Low thyroid and hair
Menopause and hair loss
Medication and lifeless hair