Low CSF/serum ratio of free T4 is associated with decreased quality of life in mild hypothyroidism – A pilot study

Abstract

Background & ObjectivePatients with mild hypothyroidismoften are depressed and have impaired quality of life despite serumfree-T4 and T3 within reference values.Therefore, we investigated whether their symptoms weredependenton the concentrations of free -T4 and T3 in the circulation and cerebrospinal fluid (CSF). MethodsTwenty-five newly diagnosed, untreatedhypothyroid subjects and as many age-and sex-matched healthy controls were investigated. Blood and CSF sampling wasperformedin the morningafter an overnight fast.Quality of life (QoL) was assessed byaLikert scale. In the hypothyroid subjects, theMADRS rating scale was also used to evaluate symptoms of depression. Furthermore, the results obtained by the questionnaireswere related toserum and CSFlevels offree- T4 and T3 as well as the ratiosbetween them in CSF and in serum. ResultsSelf-reported health was considerably lower in hypothyroid subjects.MADRS was considerably higher than the normal range for healthy individuals.Low CSF/serum free-T4ratio was correlated with an increased depressed state according to MADRS(p < 0.01),andin addition,CSF/serum free-T4 ratiocorrelated positively withthe self-reported general healthLikert scale (p < 0.05).Concentrations of TSH, or free-T3 in serum or CSF, were not associated with an increased depressed state or self-reported general health. ConclusionsLowCSF/serumratio offree-T4was correlated withimpairedgeneral health and mood, in contrast to serum measurements not showing any correlations. Thesefindings mightpartlyexplain whysomepatients with hypothyroidism suffer from mental symptoms, despite adequate serum levels of free-T4.However, the findings need to be confirmed in further and larger studies.