Prevalence of thyroid hormone abnormalities in elderly patients with symptoms of organic brain disease.

Analysis of the serum concentrations of free thyroid hormones (fT3, fT4) and thyrotropin (TSH) in 173 psychogeriatric patients (94 females and 79 males, mean age 79 +/- 8 years) disclosed that the hormone levels were related to sex, psychiatric diagnosis, medication and the presence of nonthyroid illness (NTI). Subnormal concentrations of thyroid hormones and/or TSH were found in 25% of the patients. In addition, fT3 and fT4 concentrations were significantly lower (p < 0.05 and p < 0.001, respectively) in demented males compared with demented females although the levels were within the reference limits. Strongly negative correlations between fT3 and age (p < 0.001), and between fT3 and the sedimentation rate (SR) (p < 0.01) were found in demented but not in non-demented patients. These correlations were most pronounced in (age) or restricted to (SR) demented males. In addition, the correlation between fT3 and Hb was strongly positive (p < 0.001) in demented as well as in nondemented patients, particularly in males. The concentration of fT4 was positively correlated to Hb in demented males (p < 0.001), whereas TSH concentration was positively correlated to Hb in demented females (p < 0.05). The results show that TSH is not sufficient as the sole screening assay for evaluation of possible thyroid dysfunction in psychogeriatric patients. In addition, central (hypothalamic?) hypothyroidism may be present in a substantial amount of psychogeriatric patients, as we found an adequate TSH response to exogenous thyrotropin-releasing hormone (TRH) also in patients with decreased fT3/fT4 and no signs of non thyroid diseases. Furthermore, there was an apparent lack of correlation between thyroid hormone levels and dementia (or subgroups of dementia), even though thyroid hormone abnormalities seemed to be rather common in frontotemporal dementia (38%) and non specified dementia (36%).