The objective of this study was to determine whether hypothyroidism is more common in Parkinson patients than in a control group without Parkinson, as suggested in the past. We performed a retrospective file review of all admissions to the geriatric ward during a 1-year period. Concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) from 92 Parkinson patients were compared with those of 225 randomly selected controls from the same ward. Hypothyroidism was not found to be more common in patients with Parkinson disease as previously suggested. Incidentally, we found an unexpected increase in the prevalence of abnormal thyroid laboratory tests in this group. Statistically significant differences were found in two subgroups, (1) men with Parkinson were more likely to have abnormal thyroid laboratory tests as compared with controls; and (2) 'subclinical' hyperthyroidism was found to be more prevalent in Parkinson patients than in controls. Further research in this field is warranted in non-hospitalized patients.