There have been conflicting findings on the relationship between Thyroid function and psychiatric diagnosis, in particular Mood- and Anxiety-disorders.

Our aims were: to evaluate the incidence of thyroid dysfunctions in a psychiatric sample studying their association with psychiatric diagnosis and, for Bipolar Disorder (BD), to study the association of thyroid disorders with its sub-types, phases and cycling-patterns, weighing up Lithium-therapy effect.

Carrying-out a retrospective analysis (period 2000–2010) we selected 1012 patients admitted to a University Psychiatric-Service who underwent a thyroid-hormones analysis (fT3, fT4, TSH) with or without anti-thyroid-antibodies dosage. Thence we studied the association between these laboratory-values and diagnostic categories, lithium-therapy and subtypes, phases and cycling-patterns of BD.ResultsBoth “hormonal situation” (p < 0.001) and “presence of auto-antibodies” (“Ab+”) (p = 0.001) were associated with “Diagnostic categories”; in particular “hypothyroidism” and “Ab+” were associated with BD and Borderline Personality Disorder (BPD). “Previous lithium-therapy” was associated with “hypothyroidism” (p < 0.001). Multivariate analysis showed BD, BPD and Lithium-therapy to be predictors of “hypothyroidism” and “Ab+”. We found no association between hormonal/autoimmune dysfunctions and subtype, phase or Cycling-pattern of BD.

The most relevant and novel finding of our study is that thyroid dysfunctions are associated with psychiatric disorders characterized by “high affective instability”, such as BD and BPD. Lithium could be a “trigger” of thyroid dysfunction, but it seems to play a collateral role in BD.