The Effects of Levothyroxine Replacement or Suppressive Therapy on Health Status, Mood, and Cognition

Abstract

Women receiving TSH-suppressive doses of L-T4 do not have central nervous system dysfunction due to exogenous subclinical thyrotoxicosis, but TSH-suppressed and L-T4-replaced women have slight decrements in health status and mood that may be related to self-knowledge of the presence of a thyroid condition or other uncharacterized factors. These mood alterations do not impair cognitive function.

Effect of Thyroid Function Variations Within the Laboratory Reference Range on Health Status, Mood, and Cognition in Levothyroxine-Treated Subjects

“…Two of them are sensitive measures of working memory (N-Back and Subject Ordered Pointing) (42,43). In concordance with the few available reports in non-LT4 treated (7,17) and LT4 treated euthyroid subjects (23,26,27), we did not find associations between thyroid function and these four measures.…”

“…Some studies have shown that LT4 treated subjects have decreased psychological well-being or cognitive measures compared with control groups, while other studies have reported no differences in these measures (11,(22)(23)(24)(25)(26)(27). Only four studies further investigated whether outcomes varied by TSH or thyroid hormone levels within the reference range in LT4 treated subjects, again with divergent findings (11,23,25,27).…”

“…The pattern we observed in the low-normal TSH group (consistent improvement across trials) appears similar to that reported in healthy control subjects (49), and better than the plateau observed in the highnormal TSH group. To our knowledge, this is the first report that utilized such a ''real-life'' measure of decision making in LT4 treated subjects (27). However, these results are preliminary, given our limited sample size and multiple comparisons.…”

“…However, it is not clear that targeting the lower end of the TSH reference range will achieve patients' desired outcomes. The observational literature is divergent, and there is only one controlled trial addressing this, which did not show significant effects (11,(22)(23)(24)(25)(26)(27)(28).…”

“…Published studies have attempted to document this (11,(22)(23)(24)(25)(26)(27), but it can be difficult to map these subjective complaints to specific objective domains. Our test measures most relevant for these complaints include subsets of the SF-36, POMS and ALS for fatigue and mood, as well as the Letter Cancellation and Trail Making Tests (attention, concentration, and cognitive flexibility).…”