Prevalence of depression in patients affected by subclinical hypothyroidism

The aim of this study was to estimate the prevalence of depressive symptoms in patients affected by subclinical hypothyroidism by means of Hamilton Rating Scale for Depression (HAM-D) and Montgomery-Asberg Depression Rating Scale (MADRS); to assess which depressive symptoms are prevalent in our population, with references to the factorialization of HAM-D by Cleary and Guy (1977); to verify whether levothyroxine replacement therapy alone can induce total remission of depressive symptoms.

The study enrolled 63 patients affected by subclinical hypothyroidism undergoing follow-up at the endocrinology service of San Paolo Hospital in Milan. All patients underwent an evaluation by means of HAM-D and MADRS scales and serum TSH, free T4, free T3, TPO-Ab and Tg-Ab levels were measured.

We estimated a prevalence of depressive symptoms in our population of 63.5%. Concerning the qualitative assessment of psychiatric disturbances in the population we considered, our results showed that the most frequent symptoms were part of four factors, according to the Cleary and Guy factorialization of HAM-D: these factors are representative of anxiety and somatisation (factor I), cognitive impairment disturbances (factor III), psychomotor retardation (factor V) and sleep disorders (factor VI). Levothyroxine replacement therapy alone wasn't effective in inducing total remission of depressive symptoms.

This study suggests the importance of a psychiatric evaluation in patients affected by subclinical hypothyroidism.