Mania with an organic cause: thyrotoxicosis

The psychiatric picture is mania: sustained elevated mood, racing thoughts, impulsivity and reduced need for sleep for 3 weeks. Before that is labelled bipolar disorder, an organic cause must be excluded, because a first episode of mania in a young adult has a medical cause more often than candidates expect, and treating the wrong condition harms the patient.

The examination and blood tests point to thyrotoxicosis. Tachycardia, fine tremor and dilated pupils are signs of sympathetic overactivity. A TSH of 0.01 mU/L with a free T4 of 45 pmol/L, more than double the upper limit, is unequivocal hyperthyroidism. Thyroid hormone excess causes anxiety, irritability, insomnia and, at high levels, frank mania or psychosis. The DSM-5 term is bipolar and related disorder due to another medical condition.

The energy drinks and cannabis are distractors. Caffeine causes jitteriness and palpitations, but not weeks of mania, and cannabis more often causes apathy, anxiety or psychosis. Neither explains the thyroid results. Fine tremor is also a feature of lithium toxicity and alcohol withdrawal, neither of which fits.

Management is to treat the thyroid disease: a beta-blocker for symptoms, an antithyroid drug (carbimazole), and investigation of the cause with TSH receptor antibodies and possibly a nuclear scan. Short-term antipsychotic or benzodiazepine treatment may be needed for behavioural control, but a mood stabiliser for bipolar disorder is not started at this point. Therapeutic Guidelines (Psychotropic) lists organic screening as a required step in first-episode mania.

The routine organic screen for a first manic episode includes thyroid function, full blood count, electrolytes, glucose, calcium, a urine drug screen and, if there are neurological signs, brain imaging.