Subclinical hyperthyroidism linked to increased mortality in elderly
LONDON (Reuters Health) – Elderly patients with low serum thyrotropin levels, indicative of mild thyroid hormone excess, are at increased risk of death from cardiovascular disease, European investigators report.
As reported in The Lancet for September 15, Dr. Jayne Franklyn, of the University of Birmingham in the UK, and colleagues enrolled 1191 individuals who were at least 60 years old at baseline. None of the subjects were being prescribed thyroxine or antithyroid medication. By June of 1999, 509 subjects had died.
Testing performed between 1988 and 1989 showed 71 subjects had low serum thyrotropin levels, at 0.5 mU/L or below. The investigators observed a higher mortality rate, from all causes and from cardiovascular disease, during the first 5 years of followup among those with low thyrotropin levels compared with their counterparts.
For example, at 3 years after testing, the standardised mortality ratio for the low TSH group was 2.1 for all causes and 2.2 for circulatory causes, with corresponding hazard ratios of 2.2 and 3.0, respectively
"Our findings lend support to the view that people with persistently reduced concentrations of thyrotropin in the serum should be considered for treatment (typically with radioactive iodine) to restore biochemically normal thyroid function," Dr. Franklyn's team suggests.
In a commentary, Dr. Vahab Fatourechi, of the Mayo Clinic in Rochester, Minnesota, advocates randomised studies involving patients with slightly low serum thyrotropin values in order to determine optimal treatment for such patients.
For those with undetectable thyrotropin levels, he writes, "Whether patients undergo therapy or observation should depend on the underlying abnormality, the age of the patient, and the duration of the abnormality."