Fortnightly review: Hypothyroidism: screening and subclinical diseaseBMJ 1997; 314 doi: http://dx.doi.org/10.1136/bmj.314.7088.1175 (Published 19 April 1997) Cite this as: BMJ 1997;314:1175
- A P Weetman, professor of medicinea
- a Department of Medicine, University of Sheffield Clinical Sciences Centre, Northern General Hospital, Sheffield S5 7AU
At first sight there could hardly be a more simple disorder to diagnose and treat than hypothyroidism. Now that we have robust hormone assays and reliable preparations of thyroxine in tablet sizes sufficiently small to tailor doses to an individual's requirement, what issues remain? The purpose of this review is to flesh out some of the recently published consensus views on hypothyroidism,1 2 in particular regarding the role of screening for hypothyroidism and the need for treatment in subclinical hypothyroidism. Table 1) gives the definitions of hypothyroidism.
I have conducted a monthly Medline search for all articles on hypothyroidism for five years. For this review I scanned these papers and background papers for a recent consensus statement,2 together with their references, for those focusing on screening and subclinical hypothyroidism. In addition, as part of my 15 years of thyroid related research I have continuously reviewed the literature.
Frequency of hypothyroidism
New information on the frequency of hypothyroidism has been provided by a survey of a randomly selected population of 2779 adults living in Whickham, Tyne and Wear, who had baseline thyroid function tests and were then reexamined after 20 years.3 Remarkably, 96% of the 1877 survivors participated in a follow up survey and 91% had further tests. The mean incidence of spontaneous overt hypothyroidism in women was 3.5 survivors/1000/year and in men 0.6/1000/year. There was no apparent excess of hypothyroidism in those who had died. The mean average at diagnosis was 58-59, but the probability of developing hypothyroidism increased steadily with age, reaching 14 cases/1000/year for women aged 75-80.
This survey also clarified the predictive value of detecting thyroid antibodies (against thyroid peroxidase/microsomal antigen) and measuring thyroid stimulating hormone concentrations. For women with subclinical hypothyroidism but without thyroid antibodies the relative risk of developing overt hypothyroidism over …