Synopsis

Source of validity: Scientific
Rating (out of 5): 3

Thyroid substance, often derived from desiccated animal thyroid glands, is primarily used to treat hypothyroidism—a condition where the thyroid gland does not produce enough thyroid hormones. One of the classic symptoms of hypothyroidism is hair loss or thinning, which can affect the scalp and even the eyebrows. The scientific justification for using thyroid substance in the context of hair loss is therefore indirect: by restoring normal thyroid hormone levels in individuals with hypothyroidism, hair growth often resumes, and hair loss decreases.

Several studies and clinical observations have established a clear link between thyroid dysfunction and hair health. For instance, Thyroid (2015) and other endocrinology texts document that correction of hypothyroidism with thyroid hormone replacement (including thyroid substance or levothyroxine) frequently leads to improvement or resolution of hair loss. However, there is no strong evidence that thyroid substance benefits individuals with normal thyroid function who are experiencing hair loss for other reasons (e.g., androgenetic alopecia or telogen effluvium). Use of thyroid hormone in euthyroid individuals can be dangerous and is not recommended.

In summary, the use of thyroid substance is scientifically validated for hair loss only when hair loss is a symptom of hypothyroidism, and its use is not justified for hair loss from other causes. The evidence rating is moderate (3/5) due to the specificity of its efficacy.

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