Thyroid disorders could lead to hair loss, among a host of other undesirable symptoms. According to the British Thyroid Foundation, you may experience hair loss as a side effect if you have prolonged and severe hyper- or hypothyroidism.
In general, this symptom manifests in diffuse hair loss that ultimately covers your entire scalp as opposed to distinct areas of the head. In some ways, perhaps this is a positive attribute, as the hair thins uniformly. And the good news is that individuals’ hair tends to regrow if their thyroid disorder is treated successfully, though this usually takes many months and all the lost hair may not grow back. It’s also helpful to note that mild or short-lived thyroid disorders don’t usually cause hair loss.
Another instance in which thyroid disorders could lead to hair loss, ironically, is during their treatment. Some anti-thyroid drugs–namely propylthiouracil and carbimazole–may, rarely, lead to diffuse hair loss. Often times, it’s quite difficult to pinpoint whether the hair loss is because of the thyroid’s overactivity or the drug’s side effects. This phenomenon is, however, unusual, and people very rarely seek alternative anti-thyroid treatments.
A third way in which thyroid disorders may culminate in hair loss is if one has an autoimmune thyroid disease that leads to the development of a secondary autoimmune condition. Most individuals with hyper- or hypothyroidism have an autoimmune form of thyroid disease, and people with one autoimmune disorder are likely to develop another. Alopecia areata is an autoimmune condition often developed by individuals who also have an autoimmune thyroid disorder; it leads to discrete areas of hair loss.
If you’re noticing hair loss that manifests in ways that are concerning to you, you should speak with your doctor. It’s important to note, however, that it’s rare for a thyroid disorder to cause hair loss without other manifestations of the condition. In any case, speaking with a physician will help you get to the bottom of your symptoms.