THYROID DISORDERS

• Thyroid diseases are common worldwide.
• In India too, there is a significant burden of thyroid diseases.
• According to a projection from various studies on thyroid disease, it has been estimated that about 42 million people in India suffer from thyroid diseases.
• This review will focus on the epidemiology of five common thyroid diseases in India: (1) hypothyroidism, (2) hyperthyroidism, (3) goiter and iodine deficiency disorders, (4) Hashimoto’s thyroiditis, and (5) thyroid cancer.
• This review will also briefly cover the exciting work that is inprogress to ascertain the normal reference range of thyroid hormones in India,especially in pregnancy and children.
  Key words: Hypothyroidism, India, thyroid.

INTRODUCTION

• Thyroid diseases are, arguably, among the commonest endocrine disorders worldwide.
• India too, is no exception. According to a projection from various studies on thyroid disease, it has been estimated that about 42 million people in India suffer from thyroid diseases.
• Thyroid diseases are different from other diseases in terms of their ease of diagnosis, accessibility of medical treatment, and the relative visibility that even a small swelling of the thyroid offers to the treating physician.
• Early diagnosis and treatment remain the cornerstone of management

 HYPOTHYROIDISM

• Among the various varieties of hypothyroidism, congenital hypothyroidism is probably the most important, as it is requires an early diagnosis, which is usually followed by appropriate therapy that can prevent the onset of brain damage.
• Studies from Mumbai have suggested that congenital hypothyroidism is common in India, the disease occurring in 1 out of 2640 neonates, when compared with the worldwide average value of 1 in 3800 subjects.
• There is often a delay in the diagnosis of congenital hypothyroidism in the country. This delay is attributable to the lack of awareness about the illness, as well as the lack of facilities available or screening program in place to comprehensively screen and test newborns for this illness.

HYPERTHYROIDISM

• The prevalence of hyperthyroidism has been studied in several studies.
• In an epidemiological study from Cochin, subclinical and overt hyperthyroidism were present in 1.6% and 1.3% of subjects participating in a community survey.
• In a hospital-based study of women from Pondicherry, subclinical and overt hyperthyroidism were present in 0.6% and 1.2% of subjects.
• More than a third of community-detected hyperthyroid cases have positive anti-TPO antibodies, and about 39% of these subjects have a goiter.

GOITER AND IODINE DEFICIENCY

• Recent population studies have shown that about 12% of adults have a palpable goiter.
•  Autoimmune thyroid diseaseis probably commoner than iodine deficiency as a cause of goiter in areas that are now iodine sufficient.
• However, given that iodine deficiency is a problem in India, the importance of iodine deficiency cannot be underestimated in the Indian context.
• The link between endemic goiter and iodine deficiency has been researched in India by several eminent researchers, and this has led to the publication of several important reports.
• Critical research has resulted in endemic goiter being reported from all over the country and not just from the Himalayan and Sub-Himalayan regions.
• Researchers from New Delhi had shown that this was linked to iodine deficiency and that this resulted in decompensated hypothyroidism in many cases.
• This led to landmark studies which showed that iodine deficiency was associated with hypothyroidism in neonates, setting the scene for the now legendary salt iodization program supported by the Government of India.
• Subsequent to this program, it was shown that in selected regions of Uttar Pradesh, the prevalence of congenital hypothyroidism had come down from 100/1000 to 18/1000.
• Several landmark studies have been carried out in the area of iodine deficiency disorders in the country.

SUMMARY

• Interesting work is in progress to ascertain the predictors of thyroid gland size in an Indian population.
• In a study of 1002 children from Gujarat, the authors note that the prevalence of goiter was very high (80%) when assessed by ultrasound.
• This was also a population with a high prevalence of malnutrition (82% subjects were underweight).
• In this population, the authors note that thyroid size was related to several anthropometric parameters.
• However, it is not clear whether these results are applicable to the general Indian population.
• In the state of Gujarat, the same group had reported that iodine deficiency continues to be a problem, as more than 20% of the population had a very lowmedian urinary iodine of <50 µg/l.