BACKGROUND: Clinic-based studies have indicated that older hypothyroid patients may present only few symptoms.

METHODS: In this population-based study of hypothyroidism, we investigated how the power of symptom presence predicts overt hypothyroidism in both young and older subjects. We identified patients newly diagnosed with overt autoimmune hypothyroidism in a population (n = 140, median thyroid-stimulating hormone, 54.5; 95% confidence interval [CI], 28.3-94.8; median total T4, 37; 95% CI, 18-52) and individually matched each patient with 4 controls free of thyroid disease (n = 560). Participants filled out questionnaires concerning the presence and duration of symptoms. We compared the usefulness of hypothyroidism-associated symptoms in predicting overt hypothyroidism in different age groups (young: <50 years, middle age: 50-59 years, old: ≥60 years) also taking various confounders into account.

RESULTS: In young hypothyroid patients, all 13 hypothyroidism-associated symptoms studied were more prevalent than in their matched controls, whereas only 3 of those (tiredness, shortness of breath, and wheezing) were more prevalent in old patients. The mean numbers of symptoms presented at disease onset were 6.2, 5.0, and 3.6 at the ages of 0 to 49 years, 50 to 59 years, and 60+ years, respectively. In young versus old people with 0 to 1 symptoms, the odds ratio for being hypothyroid was 0.04 (95% CI, 0.007-0.18) versus 0.34 (95% CI, 0.15-0.78) (reference all other groups). In young versus old subjects reporting ≥4 symptoms, the odds ratio for being hypothyroid was 16.4 (95% CI, 6.96-40.0) versus 2.22 (95% CI, 1.001-4.90). Receiver operating characteristic analyses revealed that the symptom score was an excellent tool for predicting hypothyroidism in young men (area under the receiver operating characteristic curve, 0.91; 95% CI, 0.82-0.998), whereas it was poor in evaluating older women (area under the receiver operating characteristic curve, 0.64; 95% CI, 0.54-0.75).

CONCLUSION: Hypothyroid symptom score is a good discriminating tool to identify hypothyroidism in young patients but fails to identify hypothyroidism in the elderly. Thus, thyroid function should be tested on wide indications in old age.