How thyroid problems affect hair
The thyroid helps regulate the growth cycle of your hair, so both an underactive (hypothyroid) and overactive (hyperthyroid) thyroid can cause hair loss. When thyroid hormones are out of balance, more hairs than normal shift into the shedding phase, leading to thinning.
This is one of the reasons a GP often checks thyroid function when someone reports hair loss.
What it looks like
Thyroid-related hair loss is usually diffuse — an overall thinning across the whole scalp rather than distinct bald patches. You might notice more hair in the brush or shower, a thinner ponytail, or a widening part. With hypothyroidism, hair can also become dry, coarse and brittle; with hyperthyroidism, it may feel fine and soft. Some people lose the outer third of their eyebrows.
Because it's diffuse, it can be subtle at first and easy to attribute to other things.
The good news
Thyroid hair loss is usually reversible. Once the thyroid problem is treated and hormone levels return to normal, hair generally regrows over several months, though it can take time and lag behind the rest of your recovery. Checking and correcting iron levels helps too, as low iron often coexists and worsens hair loss.
If you have hair loss with other symptoms (fatigue, weight or temperature changes), ask about thyroid testing. A telehealth consult can arrange the bloods and review them with you.
Related condition
Thyroid health →References & sources
- 1.Hypothyroidism — healthdirect
- 2.Thyroid gland — healthdirect
- 3.Thyroid gland — Better Health Channel
This content is general information and not a substitute for individual medical advice. Please consult a GP for your personal situation.
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