Thyrotropin level and cognitive performance: Baseline results from the ELSA-Brasil Study

Area of Science:

• Endocrinology
• Neuroscience
• Public Health

Background:

• Subtle thyroid function alterations, including subclinical thyroid disease and normal-range serum thyrotropin (TSH), have a controversial association with cognitive decline.
• This study addresses the relationship between serum TSH and subclinical thyroid dysfunction and cognitive performance in middle-aged adults without overt thyroid disease.

Purpose of the Study:

• To evaluate the association of serum TSH and subclinical thyroid dysfunction with cognitive test performance.
• To analyze data from a large sample of Brazilian middle-aged adults in the Brazilian Longitudinal Study of Adult Health.

Main Methods:

• A cross-sectional analysis included 10,362 participants aged under 65, excluding those with overt thyroid dysfunction, stroke, or specific medications.
• Thyroid status was determined by serum TSH and free thyroxine levels, with participants categorized by TSH tertiles and thyroid function (euthyroidism, subclinical hypothyroidism, subclinical hyperthyroidism).
• Cognitive function was assessed using the delayed word recall, semantic verbal fluency, and Trail Making Test Part B, with analyses adjusted for multiple confounders.

Main Results:

• The lowest TSH tertile was significantly associated with worse performance on the Trail Making Test Part B (executive function) after adjusting for confounders.
• This association remained significant even when the analysis was restricted to individuals with TSH within the normal range.
• Subclinical thyroid disease was not found to be associated with cognitive test performance.

Conclusions:

• Low serum TSH levels within the normal range are associated with poorer executive function in middle-aged adults without overt thyroid dysfunction.
• These findings suggest that even subtle variations in thyroid function may impact cognitive abilities.