Hypothyroidism and Bipolar Affective Disorder: Is There a Connection?

CONTEXT: Hypothalamic-pituitary-thyroid axis dysfunction in the pathophysiology of bipolar disorder has received less attention as compared with that in depressive disorder. AIMS: To study the prevalence of hypothyroidism in patients diagnosed with bipolar disorder and compare it with a population norm. SETTINGS AND DESIGN: The setting was the psychiatry inpatient unit of a tertiary care hospital. The design was retrospective and observational. SUBJECTS AND METHODS: A retrospective observational study was performed, referring to the case records of 84 cases of bipolar disorder admitted to the Department of Psychiatry in a Tertiary Referral Center during the year 2010-2012. The prevalence of hypothyroidism both subclinical as demonstrated by elevated thyroid stimulating hormone (TSH) levels (cut-off value 4.2 μU/ml) and overt hypothyroidism (fasting T4 <0.92 ng/dl and TSH >4.2 μU/ml) was calculated. This was compared with the population prevalence of hypothyroidism as determined by an epidemiological study carried out in the year 2009, in the same region. The correlation between hypothyroidism, gender, lithium prophylaxis and family history of mood disorder was computed. STATISTICAL ANALYSIS: Percentage prevalence of hypothyroidism in the sample was calculated and compared to a population norm. The correlation between hypothyroidism, gender, lithium prophylaxis and family history of mood disorder was computed using the odds ratio (OR). RESULTS: The total prevalence of hypothyroidism in both males and females in the bipolar group was comparable with that in the general population. There is a significant association between family history of mood disorder in first degree relatives and patients having hypothyroidism (OR 5.504 and P = 0.012). There were no statistically significant associations between thyroid abnormalities and age, duration of illness and lithium prophylaxis. CONCLUSIONS: There is no significant association between hypothyroidism and bipolar disorder. Family history of mood disorder and hypothyroidism show significant association. (OR -5.504 AND P = 0.012).