Study on prevalence of hypothyroidism in women of reproductive age in Meghalaya, North-Eastern India

I. J . Kharkongor and B. B. P. Gupta*

Environmental Endocrinology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, India

In order to study the prevalence of hypothyroidism in the women of reproductive age group (15–45 years) of Meghalaya, serum samples collected from non-pregnant and pregnant women were screened for total T4 (thyroxine) and TSH (thyrotropin) with the help of radioimmuno assay and immunoradiometric assay. In the non-pregnant women of age group 36–45 years, the prevalence of hypothyroidism was found to be 3.33%, while among pregnant women, in the age group 15–25 years a prevalence of 3.70% was recorded. When all samples were considered together, a prevalence of 1.11% and 1.43% was noted in the non-pregnant and the pregnant women, respectively. An average prevalence of 1.25% was recorded among the women of the reproductive age irrespective of status. Thus, the prevalence of hypothyroidism in the women of Meghalaya seems to be very high as compared to that of the non-endemic goitre belt of India (0.071%).

IODINE has important effects on human health and social development and its deficiency constitutes one of the major international public health problems1,2. Iodine in adequate amounts (RDA:150 µg) is a prerequisite for the biosynthesis of thyroid hormones (TH) by the thyroid gland. In case of deficiency of dietary iodine, the rate of TH biosynthesis is decreased resulting in a condition called hypothyroidism. Continued lack of iodine

*For correspondence.

in the diet leads to iodine deficiency disorders (IDD)3–5 like goitre (clinical hypothyroidism) and endemic cretinism associated with mental retardation, deafness and ataxia, lower IQ, etc.6–8. Hypothyroidism during foetal/post-natal life interferes with the normal development and maturation of the central nervous system6,9 and increases the chances of infant mortality, congenital abnormalities1,10, stunted growth and dwarfism. associated with a waddling gait, etc.6,11. Hypothyroidism during childhood results in impaired mental functions and psychology5,9. Further, in hypothyroidic individuals sexual maturation and the onset of puberty is also delayed. In adults, hypothyroidism is associated with reduced fertility12, impaired mental function1,13, coronary heart diseases and atherosclerosis6, anaemia12, pleural effusions of the respiratory system, reduced appetite, constipation, delayed muscle contraction and relaxation, decreased renal blood flow and glomerular filtration rate, etc. In pregnant women hypothyroidism leads to abortion and premature delivery1,14, still birth1,10,14 or birth of congenitally defective babies1,4,12. So far, epidemiological surveys have been conducted to study the prevalence of hypothyroidism in the population inhabiting the foothills of the Himalayas (Terai region) and Assam only, where the prevalence of hypothyroidism has been reported to be very high15–17. There is practically no information on prevalence of hypothyroidism (either clinical or sub-clinical) in the state of Meghalaya. Therefore, keeping in view the severe adverse effects of TH deficiency among the general population, particularly in women and the lack of information about the status of hypothyroidism in the state of Meghalaya, we decided to study the prevalence of hypothyroidism in women of reproductive age in Meghalaya by measuring the levels of total thyroxine (T4) and thyrotropin (TSH) using radioimmuno assay (RIA) and immunoradiometric assay (IRMA), respectively.

For this study, blood samples (5 ml from each individual) were collected with the help of disposable needles and syringes in the morning (9 to 10 am) from fasting normal (non-pregnant) and pregnant women of different age groups (Table 1).

The collected blood samples were allowed to clot at room temperature. Then the samples were rimmed and centrifuged at 2000 g (3000 RPM) for 15 min and the

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Table 1. Blood samples from women of different age groups and

serum was collected in pre-numbered capped tubes. The serum samples were stored in a freezer (–15° C to
–18° C) for measurement of hormones. The working group of the European Society for Paediatric Endocrinology has recommended measurement of the circulating levels of TSH and total T4 as the best parameters for monitoring hypothyroidism and to assess thyroid status18. Therefore, the levels of total T4 and TSH were measured in the serum samples using RIA and IRMA, respectively. The RIA and the IRMA kits were obtained from the Board of Radiation and Isotope Technology, Mumbai. The serum samples from different age groups and status were randomly selected and processed for RIA and IRMA following the instructions and protocols provided by the manufacturers. The data were analysed statistically with the help of Student’s t test and regression analysis.

The data are presented in Table 2. In non-pregnant women, the serum concentration of total T4 ranged between 47.08 ng/ml and 216.60 ng/ml (normal physiological range of T4 is 48–120 ng/ml). The average concentration of total T4 was significantly lower in the age group of 36–45 years as compared to age groups of 15–25 years and 26–35 years (Table 2). The average concentration of total T4 of all 90 samples from non-pregnant women was found to be 100.54 ±  25.11 ng/ml. The concentration of TSH in non-pregnant women ranged between 0.1 µIU/ml and 6.106 µIU/ml (normal physiological range of TSH is 0.40–7.00 µIU/ml). The average concentration of TSH of all samples from non-pregnant women was found to be 1.17 ±  0.09 µIU/ml. There was no significant difference in the concentration of TSH between the different age groups. On the basis of the level of total T4 and TSH, 3.33% women in the age group of 36–45 years were found to be hypothyroidic. In addition, several euthyroidic non-pregnant women had total T4 concentration at the border of the lower physiological limit.

In the pregnant women, the serum concentration of total T4 ranged between 29.44 ng/ml and 321.99 ng/ml (average: 167.73 ±  48.27 ng/ml), and that of TSH between 0.1 µIU/ml and 6.0 µIU/ml (average: 1.29 ±  0.09 µIU/ml). There was no significant difference in the average concentrations of T4 and TSH of different age groups of pregnant women. However, among the pregnant women of 15–25 years age group, out of twenty seven, one individual (3.70%) was found to be hypothyroidic.

In order to find out the correlation, if any, between age and the level of total T4 and TSH, the data was analysed using ‘regression analysis’ (Table 2). It was found that there was an insignificant negative correlation between age and T4 concentration of non-pregnant women (r = – 0.12). However, there was a significant positive correlation between age and the concentration of TSH in non-pregnant women (r = 0.52). In pregnant

Table 2.  Concentrations of total thyroxine (T4) and thyroid stimulating hormone (TSH) in the serum of women
of different age groups

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women, a significant positive correlation was found between age and the levels of T4 (r = 0.87) and TSH (r = 0.95).

A survey conducted in 1966 by the National Goitre Control Program reported goitre prevalence to be 23.0% in Garo hills and 7% in composite Khasi and Jaintia hills of the erstwhile Assam (now Meghalaya)19. After this study, no other survey has been conducted in the state during the last three decades. Therefore, there is practically no information about the actual status of
hypothyroidism in Meghalaya. Despite the fact that the incidence of hypothyroidism is more dangerous
in women of reproductive age group, no attention was focused on hypothyroidism in women in any of the earlier studies conducted. To the best of our knowledge, this might be the first study of its kind in India in which women (both pregnant and non-pregnant) in the reproductive age group (15–45 years) were screened for hypothyroidism by measuring the levels of T4 and TSH.

The present study recorded 3.33% prevalence of hypothyroidism in non-pregnant women of 36–45 years age group, and 3.70% prevalence of hypothyroidism in pregnant women of 15–25 years age group. Since hypothyroidism was found in individuals belonging to 15–25 years age group and 36–45 years age group, ideally pregnancy should be avoided during the early and late years of reproductive age of women. When considering the total number of samples, 1.11% prevalence of hypothyroidism was recorded among non-pregnant women and 1.43% prevalence of hypothyroidism was recorded among pregnant women. When considering all (both pregnant and non-pregnant) the samples together, 1.25% prevalence of hypothyroidism seemed to be evident in the screened population. When we compare the 1.25% prevalence of hypothyroidism in the women of Meghalaya with that of Delhi and Kerala (non-endemic goitre regions where risks of hypothyroidism is negligible (0.071%)) (ref. 15), it is about 18 times higher. However, the prevalence rate recorded in the present study is only about one-third of prevalence rate reported for the goitre districts of Uttar Pradesh15. Since information on prevalence of hypothyroidism in men and children remains unknown, there seems to be an urgent need to screen the population of Meghalaya and other adjoining states of North-Eastern India so that remedial steps can be taken up by the concerned agencies.


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ACKNOWLEDGEMENT.  We thank G.D. Hospital and Pasteur Institute, Shillong for their help in collection of blood samples

Received 3 July 1998; revised accepted 22 September 1998