Hypothyroidism and aging: The Rosses' survey

An earlier impression of a high prevalence of hypothyroidism in a general p ractice (4,190 patients including 1,544 adult females aged 18 years or more with 544 aged 50 years or more) in the Rosses, a coastal area in the north west of Ireland was confirmed by this study. The accumulated prevalence of overt spontaneous primary hypothyroidism was 8.6% in 544 females aged 50 ye ars or more but only 0.9% in the 1,000 females between 18 and 50 years of a ge. This prevalence was approximately twice that of an Irish National gener al practice population sample of 4,314 females aged 50 years or more (8.6% vs. 4.6%) p < 0.001. The reasons for this difference are unclear but may re flect the high level of opportunistic screening carried out in West Donegal . Thyroid peroxidase antibodies measured by radioimmunoassay were found in 75.6% of hypothyroid patients compared to 18.6% of practice controls (p < 0 .01). Neither HLA-DRB1, DQA1, and DQB1 phenotype frequencies nor dietary io dine intake (median urinary iodine excretion 104 mu g/L) appeared to be con tributory factors. The finding of an 8.6% accumulated prevalence of hypothy roidism in females greater than 50 years of age when a population is aggres sively investigated demonstrates the relative importance of its contributio n to total morbidity and suggests that the disorder may be underdiagnosed, thus supporting the concept of targeted screening in this age group.