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Subclinical hypothyroidism may be overestimated in nearly 20% of elderly
The prevalence of subclinical hypothyroidism may be overestimated in nearly 20% of elderly patients, except when age-specific reference intervals are used, according to data published in Thyroid Research.
These findings could have clinical implications for diagnostic accuracy and unnecessary tests, according to Rosita Fontes, MD, of Hospital Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, and colleagues.
“This study, conducted prospectively with a reference population, showed that [thyroid-stimulating hormone] increases progressively and significantly with age,” researchers wrote. “Prevalence of subclinical hypothyroidism is overestimated in the elderly, in almost 20% of subjects. … This might improve diagnostic accuracy and reduce the need of confirmatory unnecessary tests.”
The researchers examined 1,200 women and men stratified by age, excluding those with goiter or other abnormalities upon physical examination, positive thyroid peroxidase antibodies, thyroglobulin antibodies or other laboratory abnormalities.
Data indicated that TSH increased with age among all patients. However, researchers reported no statistically significant differences in the analysis of independent subgroups aged: 20 to 49 years vs. 50 to 59 years (P>.05); and 60 to 69 years vs. 70 to 79 years (P>.05).
In addition, they developed TSH reference indexes for three age groups:
• 20 to 59 years (0.4 mU/L-4.3 mU/L);• 60 to 79 years (0.4 mU/L-5.8 mU/L); and
• 80 years or older (0.4 mU/L-6.7 mU/L).
They found that free thyroxine progressively decreased significantly with age. However, after age 60 years, the same reference index was observed (0.7 ng/dL-1.7 ng/dL). Furthermore, 6.5% of patients aged 60 to 79 years and 12.5% of those aged 80 years or older would have a misdiagnosis of elevated TSH without such a reference index, the researchers wrote.
“This confirms that not all patients who have mild TSH elevations are hypothyroid and therefore would not require thyroid hormone therapy,” they wrote.
Disclosure: The researchers report no relevant financial disclosures.