Updated 2026-09-29 · Educational only, not a diagnosis
Medical facts, drug details and treatment options on this page have not been independently medically reviewed.
What it is
Both underactive and overactive thyroid can cause diffuse thinning. Hair typically improves once thyroid levels are treated.
Who gets it
More common in women; thyroid disease affects millions of Americans.
Signs to look for
- Diffuse thinning
- Dry, brittle hair (underactive)
- Fine, soft hair (overactive)
- Thinning outer eyebrows
- Tiredness, weight or temperature changes
Common causes and triggers
- Hypothyroidism
- Hyperthyroidism
- Autoimmune thyroid disease
How it is diagnosed
- Blood tests (TSH, free T4, antibodies)
Treatment and care options
These are the options commonly discussed. What suits you depends on your diagnosis — a dermatologist can help you choose.
- Treat the thyroid with your doctor
- Check iron and vitamin D
- Supportive hair care; Minoxidil if pattern loss coexists
Outlook
Good once levels are stable, though regrowth takes months.
When to see a doctor
If thinning comes with fatigue, weight change, palpitations or feeling cold.
Frequently asked questions
Does thyroid medicine cause hair loss?
Shedding can happen when doses change, but it usually settles.
Not sure what's behind your thinning?
This content is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease. Speak with a qualified healthcare professional about your individual situation.