Parathyroid diseases can present with psychiatric symptoms and can be recognized through determinations of serum electrolytes, especially the calcium level. Psychiatric evaluations should include a serum calcium concentration test, which is also essential in reassessment of patients poorly responsive to mental illness treatment. A magnesium and a phosphate assay may also be diagnostically helpful. Abnormality of divalent cation levels may provide evidence for consideration of, or ruling out, parathyroid disorders. Determinations of parathyroid hormone are performed if clinically indicated, and if abnormal divalent cation quantifications are confirmed. If parathyroid disease is identified, corrective endocrine therapies may diminish or even cure psychiatric aspects of parathyroid pathology. Failure to recognize a parathyroid disorder leaves an endocrine-induced mental dysfunction without proper treatment.