Postpartum psychosis with an organic contributor

Postpartum psychosis is a psychiatric emergency. It affects about 1 to 2 in 1000 births, usually begins within the first 2 weeks, and is strongly linked to bipolar disorder. Command hallucinations to harm the baby carry a real risk of infanticide and suicide, so the immediate priorities are the safety of the mother and infant, admission (ideally to a mother-baby unit), and urgent psychiatric assessment. If she declines admission, the Mental Health Act applies.

Alongside safety, every new psychosis needs an organic screen, and this one has an obvious finding: a TSH of 18.2 mU/L with a low free T4 is overt hypothyroidism. Severe hypothyroidism can cause depression, cognitive slowing and, rarely, psychosis, historically called 'myxoedema madness'. In the postpartum period the likely cause is postpartum thyroiditis or a pre-existing autoimmune thyroid disease that was suppressed during pregnancy.

Thyroid disease does not fully explain everything (tachycardia and tremor are unusual in hypothyroidism), and it does not replace the psychiatric diagnosis. But of the options offered it is the only one with clear biochemical evidence and a recognised link to psychosis, and treating it is part of her care. The COPE perinatal mental health guideline recommends thyroid function testing in any postpartum mood or psychotic disorder.

Endometritis would present with fever, uterine tenderness and offensive lochia; the raised CRP alone after a caesarean is non-specific. Electrolytes and urine are normal. Her mild anaemia does not cause psychosis.

Treatment combines thyroxine replacement, an antipsychotic (with breastfeeding considered when choosing the drug), a mood stabiliser if bipolar disorder is diagnosed, and supervised contact with the baby. Recurrence risk in future pregnancies is high, so planning for the next pregnancy starts now.