Your hair is not what it used to be. It is thinner, it does not grow as fast, and you are seeing more scalp than you used to. You assumed it was genetic and there was nothing to be done. That is partially true — androgenetic alopecia (pattern hair loss) is indeed partly genetic and partly hormonal. But there are also reversible causes of hair thinning that are frequently missed, and addressing them can slow, stop, or partially reverse the process.
The Iron Connection
Iron deficiency is one of the most common causes of hair thinning, and it is the first thing to investigate when hair starts to change. Iron is required for the production of haemoglobin, the protein in red blood cells that carries oxygen to tissues. The hair follicle is one of the most metabolically active tissues in the body — it requires constant blood supply and oxygen to produce hair. When iron stores are low, the body prioritises oxygen delivery to vital organs over hair production, and the result is increased hair shedding and reduced hair growth.
The test to ask for is ferritin — the marker of iron stores. Standard NHS testing often stops at haemoglobin and serum iron, which can be normal even when ferritin is low. For women, ferritin should ideally be above 70 to 90 for optimal hair health, even though the lab reference range may say anything above 10 is normal. Low ferritin with normal haemoglobin is called iron deficiency without anaemia, and it is one of the most treatable causes of hair loss in women.
Thyroid and Hair Loss
Both hypothyroidism and Hashimoto is thyroiditis (the autoimmune form of hypothyroidism) are associated with hair thinning. The hair loss from thyroid disease is diffuse rather than patchy — you lose hair from all over the scalp rather than developing distinct bald patches. Thyroid-related hair loss is usually accompanied by other symptoms: dry skin, cold intolerance, weight gain, fatigue, constipation. If you have these symptoms alongside hair thinning, thyroid testing is warranted.
The most comprehensive thyroid testing includes TSH, free T4, free T3, and thyroid antibodies (TPO and TG antibodies). Standard NHS testing typically only measures TSH and sometimes free T4, which misses the large proportion of thyroid dysfunction that involves normal TSH but abnormal T4 or T3, or elevated antibodies in the pre-clinical stage of autoimmune thyroid disease.
What You Can Do Today
Request a full iron panel including ferritin — do not accept being told that a normal haemoglobin means your iron is fine. If ferritin is below 70, supplement iron at a dose your doctor recommends after reviewing your full iron studies. Address gut health if you have iron deficiency without clear dietary cause — gut inflammation and low stomach acid both impair iron absorption and are common hidden contributors. For thyroid, request the full panel including antibodies. These are straightforward investigations that take a blood test and a conversation, and they can identify the difference between genetic hair loss that requires cosmetic management and a reversible nutritional cause.
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Thyroid and Hair Loss
Both hypothyroidism and Hashimoto is thyroiditis (the autoimmune form of hypothyroidism) are associated with hair thinning. The hair loss from thyroid disease is diffuse rather than patchy — you lose hair from all over the scalp. Thyroid-related hair loss is usually accompanied by other symptoms: dry skin, cold intolerance, weight gain, fatigue, constipation. The most comprehensive thyroid testing includes TSH, free T4, free T3, and thyroid antibodies. Standard NHS testing typically only measures TSH, which misses a large proportion of thyroid dysfunction.
What You Can Do Today
Request a full iron panel including ferritin — do not accept being told that normal haemoglobin means your iron is fine. If ferritin is below 70, supplement iron at a dose your doctor recommends. Address gut health if you have iron deficiency without clear dietary cause — gut inflammation and low stomach acid both impair iron absorption. For thyroid, request the full panel including antibodies. These are straightforward investigations that take a blood test and a conversation, and they can identify the difference between genetic hair loss and a reversible nutritional cause.
Beyond iron and thyroid, biotin deserves attention for hair health. Biotin deficiency — which can be caused by raw egg consumption (avidin in raw eggs binds biotin), long-term antibiotic use, or gut dysbiosis — produces hair loss that reverses with biotin supplementation. The hair uses biotin for keratin synthesis. Biotin at 2.5 to 5mg daily has been shown to reduce hair shedding and improve hair quality in people with biotin deficiency. Most people are not genuinely deficient, but the supplement is extremely safe, and if hair is a concern, it is worth trying.
Selenium deficiency is also relevant to hair health, particularly in the context of thyroid function. Selenium is required for the conversion of T4 (the storage form of thyroid hormone) to T3 (the active form), and selenium deficiency produces a pattern of normal T4 with low T3 that is frequently misdiagnosed as euthyroid. Hair loss is a common feature of this pattern. Brazil nuts are the richest dietary source of selenium — two to three Brazil nuts daily provides the recommended intake — and this is one of the simplest hair health interventions available.
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