ABSTRACT By exploring postsynaptic dopamine receptor sensitivity at the hypothalamic-pituitary level, neuroendocrine responsiveness to the apomorphine (APO) challenge test provides an indirect measure of central dopamine function. The goal of this narrative synthesis is to summarize recent evidence on hormonal response to APO in patients with affective and psychotic disorders. Electronic searches were conducted in PubMed and Google Scholar to select potential papers that address the effects of APO on pituitary and hypothalamic hormones in affective disorders (major depression, bipolar disorders) and also in acute and chronic psychotic disorders. Bipolar disorder patients revealed disturbances in post-synaptic dopamine D2 receptor sensitivity mediated by prolactin secretion from the pituitary gland. Depressed patients showed a similar hormonal response to APO as healthy controls when thyroid stimulating hormone (TSH) levels were low, suggesting a contributory role for thyroid hormone in depression. Antipsychotic-naïve schizophrenia patients showed a blunted hypothalamic-pituitary-adrenal axis (HPA) response to APO when compared to healthy controls. The paranoid form of chronic schizophrenia elicited a lesser hormonal response than that seen in disorganized schizophrenia. The results of this synthesis suggest that APO response differentiates among symptomatic profiles in schizophrenia and affective disorders. It may also be able to predict treatment outcomes and guide clinicians toward antidepressants or antipsychotics with efficacy for specific disorder subtypes.
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