A study showed the Quality of life, mood and cognition were unaffected by adjusting levothyroxine dose to achieve thyroid-stimulating hormone levels near the reference range in adults with hypothyroidism. They evaluated 138 adults with hypothyroidism and normal TSH levels (mean age, 49.2 years; 91% women; 92% white; mean duration of levothyroxine treatment.

Researchers estimated 138 adults with hypothyroidism and normal TSH levels (mean age, 49.2 years; 91% women; 92% white; mean duration of levothyroxine treatment, 11.9 years; mean baseline levothyroxine dose, 1.44 µg/kg) to determine whether variations in thyroid function within and near the reference range affect quality of life, mood or cognition.

Researchers adjusted participants’ levothyroxine doses to achieve low-normal (n = 46; mean levothyroxine dose, 1.5 µg/kg), high-normal (n = 47; mean levothyroxine dose, 1.32 µg/kg) or mildly elevated TSH levels (n = 45; mean levothyroxine dose, 0.78 µg/kg) over 6 months.

Quality of life was measured using the SF-36 and Underactive Thyroid-Dependent Quality of Life Questionnaire; the mood was measured using the Profile of Mood States (POMS) and Affective Lability Scale, and cognition was measured through cognitive tests administered by a single experienced research assistant.

Participants in the low-normal TSH group compared with the high-normal TSH group had higher SF-36 Physical Functioning (49% vs. 26%; = .03) and POMS anger subscales scores (4.9 vs. 3.6; = .03); however, after correction for multiple testing, the differences were no longer statistically significant. No other measures of health status of mood differed among the three groups.

With each 1-mg/L increase in TSH, the SF-36 Mental Health subscale decreased by 0.33 points when TSH, free thyroxine, and free triiodothyronine were used as continuous variables, indicating the worsening quality of life. After correction for multiple testing, differences in cognitive function were no longer significant between the three groups.

They found no relevant differences in health status, mood, memory or executive functions in hypothyroid subjects when [levothyroxine] doses were altered in a randomized, blinded fashion to achieve TSH levels in the low-normal, high-normal or mildly elevated range.

Given our limited sample size, further studies would be helpful, particularly in targeted populations (ex. symptomatic subjects, subjects with low T3 levels, or subjects with genetic polymorphisms that affect thyroid hormone action). In the absence of definitive data, reasonable expectations should be discussed with treated hypothyroid patients who report symptoms in these areas and request higher doses or alternative thyroid hormone preparations.