Hypothyroidism can often be misdiagnosed as psychiatric illness. The hypothyroid patient may present with depression, an organic mental disorder, apathy and/or frank psychosis (usually with paranoid symptoms). Psychiatric manifestations of the endocrinopathy will abate with thyroid hormone replacement therapy, unless the disease state has been sufficiently prolonged to cause some irreversible brain damage. This irreversibility mandates prompt diagnosis and specific hormonal replacement therapy. Thus, thyroid function screening is recommended for patients presenting with depression, psychosis or organic mental disorder.