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Hypothyroid Symptoms Fail to Predict Thyroid Insufficiency in Old People: A Population-Based Case-Control Study

nurse sitting with an elderly patient

 

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.

The immune system is altered in the aging process. It becomes less responsive to antigenic challenges with an increase in incidence and morbidity of infections probably due to signaling defects in the aging adaptive immune system. On the other hand, the innate immune system is activated in old age,1 and the occurrence of autoimmune disorders increases. Moreover, increased concentration of inflammatory cytokines causing a proinflammatory environment may accelerate and complicate degenerative diseases.

Organ-specific autoantibodies are rather common among old people. Thus, old age is complicated by an increase in autoimmune disease frequency. Hypothyroidism is no exemption, and in a previous population-based study, we have calculated the median age at disease onset to be 67.6 years. Compared with people aged 0 to 30 years, hypothyroidism was diagnosed 14 times more often in those aged 50 to 60 years, and 33 times more frequently in those aged more than 70 years. This overrules by far the risk associated with female gender, the somewhat higher risk associated with genetic predisposition, and a number of environmental factors, such as iodine intake, smoking habits, alcohol abstinence, and previous live births.

Hypothyroidism may present with a variety of symptoms reflecting the hormonal insufficiency in different organs. However, none of these symptoms have high sensitivity or specificity when compared with euthyroid control persons, and previous studies have suggested scarceness of symptoms specific for hypothyroidism in the older population. Furthermore, old people also may have a variety of other diseases, and the coexistence of thyroid disease and other comorbidities challenges which symptoms may represent which disease.

We performed a study of patients newly diagnosed with overt autoimmune hypothyroidism and aimed to investigate in detail the relative frequency and importance of various symptoms at different ages of disease onset. In particular, we evaluated the usefulness of symptoms when deciding who should have their thyroid function biochemically tested, focusing on the importance of patients’ age. We previously found that symptom presence was more predictive for hypothyroidism in women than in men and now studied if such sex difference was age-dependent. Four of 5 patients (79.5%) newly diagnosed with hypothyroidism are women, and approximately more than half (56.5%) are aged more than 60 years. Thus, the usefulness of symptom screening before biochemical thyroid testing is pivotal in the geriatric patient.

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-Allan Carlé, MD, PhD, Inge Bülow Pedersen, MDSci, PhD, Nils Knudsen, MDSci, PhD, Hans Perrild, MD, Lars Ovesen, MD, Stig Andersen, MDSci, PhD, Peter Laurberg, MDSci

This article originally appeared in the October 2016 issue of The American Journal of Medicine.

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