Abstract
Of 98 patients studied prospectively during admission to the psychiatric ward of a general hospital, 13% showed an initial transient elevation of the serum thyroxine (T4) level (range 142–174 nmol/l) with the incidence increasing to 15% on serial testing at days five and fourteen. There was no clinical evidence of a thyrometabolic disorder and, as the mild hyperthyroxinaemia normalised rapidly, recourse to other thyroid function tests was not required. The possible causes of the transient hyperthyroxinaemia are discussed, but examination of the hyperthyroxinaemic patients' diagnoses did not reveal anything in common. These data indicate that the results of routine thyroid function tests in acute psychiatric admissions should be interpreted with care, and that historical and physical examination remains the primary avenue of diagnosis of thyroid disorders.