Psychiatric Manifestations of Hypothyroidism

Volume-1 Issue-2 August, 2011

A clinical syndrome of thyroid hormone deficiency is represented in the literature as a stereo typical cluster of symptoms and signs. But the clinical presentation is diverse, complicated and often overlooked. The hypothyroid state serves as a potential basis for multiple somatic complaints and psychological disturbances. At times psychiatric manifestations may be the presenting feature.
Brain has a unique sensitivity to thyroid hormones and to utilize it differently than from other system with hormone receptors being located within neural network throughout the brain. High concentration of T3 receptors are found in the amygdala and hippocampus. The effects of thyroid hormone deficiency on brain function are variable at different stages of life. The psychiatric disturbances may be in the form of affective disorders, anxiety disorders, cognitive dysfunction and even psychosis.

Affective disorders:

(a) Depression: is one of the commonest forms of psychiatric manifestations. The origin of depression in hypothyroidism appears to relate to the role of thyroxine in serotonergic transmission, such that reduced thyroid input reduces serotonergic tone & lowers the threshold toward the development of depressive symptoms. Low mood, fatigue, anhedonia, reduced concentration, and hypersomnolence are the most commonly described features of the depressive syndrome in hypothyroidism. Thyroid hormone abnormities may occur without overt functional hypothyroidism. Designated as ‘Subclinical Hypothyroidism’, these scenarios can be further classified into elevated TSH without changes in thyroid hormones (grade II hypothyroidism), abnormal TSH response to stimulation with TRH (grade III), & the presence of antithyroid antibodies with no thyroid hormone system abnormalities (grade IV) . Grade II hypothyroidism has been associated with depressive disorders.

(b) Bipolar disorder: Hypothyroidism adversely affects the course of bipolar disorder and it may serve as a risk factor for the development of the rapid cycling form of bipolar disorder. There is also evidence that significant number of patients on lithium therapy for bipolar disorder have hypothyroid states which ranges from ‘Minimal Thyroid Insufficiency (MTI)’ to frank hypothyroidism.

The probability of underlying hypothyroid status is more when the presentation is only subsyndromal depressive symptoms; treatment resistant depression; rapid cycling affective disorder or atypical depression.
Anxiety disorders – though less common than seen in hyperthyroidism, around 30 % of hypothyroid patients tend to have anxiety symptoms in them, which should be probed.

Psychosis: The first description of myxoedema madness, a typical example of hypothyroid induced psychosis was given by Ashes (1949). There is considerable variation in clinical psychotic presentation. Psychosis typically occurs after the onset of physical symptoms, after a period of months to years. It can occur even in sub-clinical hypothyroidism indicating that psychosis maybe unrelated to the absolute degree of thyroid hormone deficiency. Onset is usually acute/subacute, fluctuating course with predominant paranoid feature. In clinical practice, it is likely that most of the psychotic symptoms in hypothyroidism will accompany a mood disorder (depression or mania), dementia or delirium.
Cognitive disorders: Cognitive decline due to hypothyroidism state can cause significant functional disability and it represents one of the reversible forms of dementia in the older age group.

Management: Investigations that would help in managing such cases are Thyroid profile – Measurement of thyroid hormones TSH, Free T4 & Free T3; Antimicrosomal & Antithyroglobulin for Autoimmune thyroid disease. The EEG-reduction in alpha wave activity and PET-decrease in cerebral blood flow and cerebral glucose metabolism serve as research tools to further understand the pathogenesis. While thyroid replacement (Thyroxine) forms the definitive treatment for overt hypothyroidism and selected cases of subclinical states, judicious use of antianxiety, antipsychotic and antidepressants carries significance in managing relevant psychiatric co-morbidity. Thyroid replacement should be started early as delay results in incomplete remission. Low starting dose and gradual titration of thyroid hormone is recommended or else an exacerbation of psychosis may occur.

Hypothyroidism has protean psychiatric manifestations which needs to explored and managed. Routine thyroid function testing of psychiatric patients is not necessary but certain population should be screened like:
a) Patient with signs and symptoms of overt hypothyroidism b) Rapid cycling bipolar disorder c) Treatment refractory depression d) Patient on Lithium e) Within 6 months of delivery or women older than 44years