Thyroid-Stimulating Hormone (TSH)
TSH is the pituitary hormone that regulates thyroid activity. The median TSH in the US adult population is approximately 1.25 mIU/L, with values rising slightly with age and showing a wide population spread.
Unit: mIU/L · 12 slices · age and sex · 1 source
Filed under panels: Thyroid Panel · topics: Endocrine
Thyroid-stimulating hormone (TSH) is secreted by the pituitary gland and controls thyroid hormone production. It is the primary screening marker for thyroid function. TSH follows a log-normal distribution in the population, meaning the distribution is right-skewed and the upper tail is long. These population distributions exclude participants with self-reported thyroid disease or current thyroid medication use.
Population Distribution
Browse by Demographic
| Age (years) | male (mIU/L) | female (mIU/L) |
|---|---|---|
| 20-29 | 0.5–3.4 (1.4) | 0.5–3.3 (1.3) |
| 30-39 | 0.6–3.7 (1.3) | 0.5–4 (1.5) |
| 40-49 | 0.6–3.5 (1.5) | 0.6–3.6 (1.6) |
| 50-59 | 0.6–3.6 (1.7) | 0.5–3.9 (1.6) |
| 60-69 | 0.6–5.3 (2) | 0.7–3.3 (1.7) |
| 70+ | 0.8–4.3 (1.8) | 0.7–4.3 (1.9) |
Frequently Asked Questions
Why is the TSH distribution right-skewed?
TSH is regulated on a logarithmic scale: small absolute changes in thyroid hormone produce large proportional changes in TSH. This produces a right-skewed distribution where most people cluster at lower values but the upper tail extends considerably.
Why does TSH rise with age?
The upper end of the population distribution shifts upward with age, partly because thyroid function slows gradually and partly because subclinical hypothyroidism becomes more prevalent. Even after excluding people with self-reported thyroid disease, residual subclinical variation contributes to higher values in older age groups.
Why are males and females shown separately?
Females have higher rates of autoimmune thyroid conditions, which shifts the TSH distribution upward even in a population that excludes self-reported diagnoses. Subclinical or undiagnosed thyroid autoimmunity contributes to sex differences in the distribution.