Progression of subclinical hypothyroidism to overt thyroid dysfunction

January 01, 0001

Progression of subclinical hypothyroidism to overt thyroid dysfunction

Very few studies have assessed both the incidence and progression of thyroid dysfunction in a single older population-based cohort. In this study, the researchers aimed to assess the 5-year incidence, progression and risk factors for development of thyroid dysfunction in an older Australian population. The Blue Mountains Eye Study is a longitudinal population-based cohort study. During 1997-1999, 1768 participants (aged 55 years and above) had thyroid function assessed. After excluding participants reporting any form of treatment for their thyroid condition at baseline, 951 participants (91.4%) without thyroid dysfunction and 54 (5.4%) with thyroid dysfunction were re-examined 5 years later. Thyroid dysfunction was defined using serum thyrotropin (thyroid stimulating hormone, TSH) screen, followed by serum free T4 assessment.

The overall 5-year incidence of thyroid dysfunction was 4.7%. Obesity (body mass index greater than or equal to 30 kg/m2) and serum TSH greater than 2 mIU/L at baseline predicted incident overt hypothyroidism (odds ratio (OR) 4.05) and (OR 5.46) respectively. The 5-year incidence of subclinical hypothyroidism was significantly higher in women than in men, 2.5% versus 0.7% (significant). Progression to overt hypothyroidism was observed in 17.9% of subjects with subclinical hypothyroidism over 5 years.

The researchers concluded: "The 5-year incidence of thyroid dysfunction in this older population was relatively low, and was associated with obesity and serum TSH level greater than 2 mIU/L at baseline. Over one in six persons with subclinical hypothyroidism progressed to overt thyroid dysfunction over the 5-year period. Our findings highlight the need for appropriate management of subclinical hypothyroidism among older people."

Good to see some basic epidemiology over time. Is age 55 and above now the age of an "older" person?

For the full abstract, click here.

Internal Medicine Journal 40(9):642-649, September 2010
© 2010 Royal Australasian College of Physicians
Five-year incidence and progression of thyroid dysfunction in an older population. B. Gopinath, J. J. Wang, A. Kifley et al. Correspondence to Bamini Gopinath: [email protected]

Category: T. Endocrine/Metabolic/Nutritional. Keywords: thyroid dysfunction, incidence, progression, thyrotropin, thyroxine, Blue Mountains Eye Study, longitudinal population-based cohort study, journal watch.
Synopsis edited by Dr Stephen Wilkinson, Melbourne, Australia. Posted on Global Family Doctor 8 October 2010

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