TSH reference range in older adults: a Brazilian study

Area of Science:

• Endocrinology
• Geriatrics
• Clinical Chemistry

Background:

• Thyroid dysfunction is common in the elderly.
• Establishing population-specific reference values for thyroid-stimulating hormone (TSH) is essential for accurate diagnosis.
• Existing TSH reference ranges may not be optimal for the Brazilian elderly population.

Purpose of the Study:

• To determine serum TSH reference values in healthy Brazilian elderly individuals (70-85 years).
• To compare these values with those established for the adult population.
• To provide updated TSH reference ranges for geriatric endocrinology in Brazil.

Main Methods:

• A cross-sectional study involving 360 healthy elderly volunteers (180 males, 180 females) aged 70-85 years.
• Exclusion criteria included known thyroid disease, risk factors for thyroid dysfunction, interfering medications, goiter, thyroid nodules, positive anti-thyroperoxidase antibodies, or altered free T4 levels.
• Serum TSH levels were measured, and percentiles were calculated.

Main Results:

• The 2.5th and 97.5th percentile TSH values for the Brazilian elderly were 0.2 mIU/L and 4.62 mIU/L, respectively.
• A significant proportion of participants had TSH levels above common adult reference limits: 25.26% had TSH > 2.5 mIU/L, 15.26% had TSH > 3 mIU/L, and 6.1% had TSH > 4 mIU/L.
• TSH values in the elderly cohort were observed to be slightly higher than those previously reported for younger adult populations.

Conclusions:

• The study suggests an upper limit for normal TSH of approximately 4.6 mIU/L for the Brazilian elderly population.
• These findings indicate that current adult TSH reference ranges may lead to underdiagnosis of subclinical hypothyroidism in Brazilian older adults.
• Implementation of these age-specific reference values can improve the accuracy of thyroid function testing in this demographic.