Frances1 16

Screening the vulnerable for thyroid dysfunction

Mild hypothyroidism describes the condition where the plasma levels of thyroid stimulating hormone (TSH) are above the ‘normal’ upper limit (which is still a subject of debate) but where there is no equivalent change in circulating levels of the thyroid hormones tetraiodothyronine (T4) and triiodothyronine (T3). Many studies have concluded that since the majority of patients suffering from mild hypothyroidism have few signs and symptoms of thyroid dysfunction and that eventual overt disease is not inevitable, screening is not cost-effective except during pregnancy or in cases where there is a family history of thyroid disease or prior thyroid dysfunction. However there are two groups of people, namely menopausal women and subjects with Down syndrome (DS), who are particularly at risk and who may have difficulty recognising symptoms of overt disease should they occur. Might it not be prudent to screen these high-prevalence populations on a regular basis?
Various studies have shown that by the age of 50 around 10% of women have some symptoms of hypothyroidism, and by the age of 65 the prevalence in women is in the range of 15-20%. Not only is hypothyroidism an insidious condition, but several of the symptoms are also commonly associated with the menopause, including fatigue, sleep disturbances, weight gain, mild cognitive impairment and depression. It is thus likely that many older women with thyroid dysfunction do not seek help, and several studies have shown that many remain undiagnosed even if such help is sought. Indeed a survey by the American Association of Clinical Endocrinologists found that only a quarter of women who had discussed their menopausal sysmptoms with a physician were tested for thyroid function, though it is know that these symptoms are greatly alleviated when euthyroidism is maintained.
While routine screening detects the increased prevalence of congenital hypothyroidism in neonates with DS, thyroid dysfunction presenting later affects around five percent of DS children and over ten percent of adults. Clinical diagnosis in this group is problematic, since the DS phenotype can mask clinical features of thyroid disease, and such symptoms may also be attributed to the syndrome itself. In addition some patients may not be able to articulate their symptoms effectively.
So surely the regular screening of older women and subjects with Down syndrome is warranted to ensure that overt thyroid disease is avoided or treated promptly should it occur.