Indian Write-Ups

Screening For Thyroid Disease In The Community

The word 'screening' implies the use of a test to detect disease in a population of subjects who have no clinical evidence of the disease. Currently, no major medical organization recommends routine screening for thyroid disorders in the general community. The only screening programme that is being enforced in several countries is screening for congenital hypothyroidism in neonates. There is virtually no debate about the efficacy and importance of such a screening programme.

Screening programmes worldwide result in annual detection of more than 2500 cases in 10 million neonates screened. Congenital hypothyroidism occurs in about 1 in 4000 live births and has a female to male ratio of about 2 to 1. Four to fifteen percent of neonates in iodine deficient parts of India have been found to have clinical hypothyroidism. A screening programme on 12057 neonates using cord TSH as a screening technique in Mumbai which is a non-endemic area, in 1982-84 had found the incidence of congenital hypothyroidism to be 1:2482. The significance of screening neonates lies in the following :

• Screening programmes effectively eliminate mental retardation resulting from congenital hypothyroidism in detected neonates.
• Less than 5% of affected infants are diagnosed on clinical grounds before the screening report.
• Infants, with marked thyroid hormone deficiency, if untreated, will lose 3-5 IQ monthly during the first 6-12 months of life.
  Inspite of the overwhelming medical support for screening neonates, it is distressing that no such programme exists in our country. Even paediatricians in the metros rarely, if ever, screen neonates (including their own!) for congenital hypothyroidism. Total T4 and/ or TSH is employed, usually by heel prick, preferably at 3-5 days after birth by which time, the physiological surge in TSH that follows birth usually subsides.
  
  

Considering the epidemiology of thyroid disorders in the community, the following may be said with regards screening adults in the general population :

• It is unlikely that screening for overt thyroid disease in men of any age would be cost-effective.
• It is unlikely that screening for overt disease in healthy women of any age would be cost-effective, although screening elderly women in the clinic or in geriatric centres may have some merit.

Routine screening of apparently healthy people is generally not recommended, even in those over 60 years and with a family history of thyroid disease. Reasons include a relatively low point prevalence of overt disease and uncertainty over the benefits of detecting subclinical hypothyroidism. However, a computer-based decision model recently came to the conclusion that it is comparatively cost-effective to screen persons in the general community for mild thyroid failure with a serum TSH level combined with a serum cholesterol level every 5 years, beginning at age 35 years.

Thyroid Disease Burden In High-risk Situations

Elderly, those with Down's syndrome and post partum women are examples of high-prevalence populations. About one-thirds of elderly thyrotoxic individuals show ‘apathetic’ presentation wherein there is anorexia and muscle weakness. Conversely, symptoms of hypothyroidism like constipation, fatigue, dry skin and poor mentation may be ascribed to ageing itself. Screening persons 60 years or older in the clinical setting detects previously unsuspected hyperthyroidism in 0.1-0.9% and hypothyroidism in 0.7-2.1%.

Slow speech, thick tongue and slow mentation are seen both in hypothyroidism and Down's syndrome. Screening individuals with Down’s syndrome has detected previously unrecognized thyroid disease, primarily hypothyroidism, in 2.9% (range 0.6-5%). Screening reveals thyroid dysfunction, mainly thyroiditis in 4-6% of post partum women. Here again, fatigue, palpitations, depression are mistakenly attributed to the post partum condition.