Background Interpretation of thyroid function tests during pregnancy needs trimester-related reference intervals from pregnant populations with minimal risk for thyroid dysfunction. While India has become iodine sufficient after two decades of salt iodisation, there is no normative data for thyroid function from healthy pregnant women of this country.Aims and objectives To determine trimester-specific reference ranges for free triiodothyronine (FT 3 ), free thyroxine (FT 4 ) and thyrotropin (TSH) from healthy pregnant Indian women.Design Cross-sectional study in a reference population of pregnant women.Setting Primary care level obstetric department in India.Population Women with uncomplicated pregnancy in any trimester.Methods Five hundred and forty-one apparently healthy pregnant women with uncomplicated single intrauterine gestations reporting to the Armed Forces Clinic in any trimester were consecutively recruited. Clinical examination, thyroid ultrasound for echogenicity and nodularity and estimation of FT 3 , FT 4 , TSH and antithyroid antibodies (antithyroperoxidase [anti-TPO] and antithyroglobulin [anti-Tg]) using electrochemiluminescence technique were carried out. From this entire sample, a disease-and risk-free reference population was obtained by excluding those with any known factor that could affect thyroid function or those who were being treated for thyroid dysfunction.Main outcome measure None.Results Of the 541 consecutive pregnant women in different trimesters enrolled for the study, 210 women were excluded. The composition of reference population comprising 331 women was 107 in first trimester, 137 in second trimester and 87 in third trimester. The 5th and 95th percentiles values were used to determine the reference ranges for FT 3 , FT 4 and TSH. The trimester-wise values in the first, second and third trimesters were: FT 3 (1.92-5.86, 3.2-5.73 and 3.3-5.18 pM/l), FT 4 (12-19.45, 9.48-19.58 and 11.32-17.7 pM/l) and TSH (0.6-5.0, 0.44-5.78 and 0.74-5.7 iu/ml), respectively. Analysis of mean, median values for FT 3 , FT 4 and TSH between each trimester showed no significant difference in FT 3 and TSH values (95% CI). However, FT 4 showed significant variation between trimesters with values decreasing with advancing gestational age (P value: first versus second = 0.015, first versus third = 0.003 and second versus third = not significant). Women with antibody positivity and hypoechogenicity of thyroid gland had significantly higher TSH values when compared with women with antibody negativity and normoechogenicity.Conclusions Reference ranges of FT 3 , FT 4 and TSH have been established for pregnant Indian women using 5th and 95th percentiles.

Subjects with goitrous autoimmune thyroiditis need periodic monitoring of thyroid function. Development of thyroid dysfunction is insidious and may not be accompanied by symptoms and clinical signs. In pediatric and adolescent age groups it is imperative to correct thyroid dysfunction to achieve optimal growth and development.

Autoimmune thyroiditis is a frequent cause of goiter in children and studies point to the increasing prevalence of juvenile autoimmune thyroiditis (JAT) in children and adolescents. Clinically, JAT can manifest, depending on the presence or absence of goiter, as either a goitrous form or atrophic form. Both are characterized by the presence of thyroid antibodies in serum, with the goitrous form being more common in children. Recent evidence suggests that thyroid autoimmunity originates from an interaction of genetic, endogenous and environmental factors which end up activating thyroid-specific autoreactive T-cells in susceptible children. In addition to underlying genetic/HLA predisposition, factors including sex hormones, glucocorticoids, low birth weight, radiation and drugs may play a role in thyroid autoimmunity. Patients with JAT can present due to thyroid enlargement or symptoms arising due to hypothyroidism. Asymptomatic enlargement of the thyroid gland is a common presenting complaint, especially in older children and adolescents. Thyroid function can vary from euthyroidism to subclinical or overt forms of hypothyroidism and less commonly hyperthyroidism. Accordingly, patients can be symptomatic. There is considerable debate regarding the management of patients with euthyroidism or subclinical hypothyroidism. Available evidence indicates the presence of residual goiter in endemic form and a high prevalence of JAT in children. It is suggested that children should be screened for goiter as part of school health examinations, and goitrous children should be monitored for thyroid function.

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Delhi lies in the sub-Himalayan plains and the existence of iodine deficiency is well established. Iodised salt was introduced in Delhi nearly two decades ago. The aim of the present study was to determine the status of iodine nutrition in school-aged children and the prevalence of autoimmune thyroiditis. A total of 4,320 schoolchildren (2,218 [51.3%] boys) aged 10-16 years were studied. Goitre was detected in 396 children, an overall goitre prevalence of 9.2%. Of the 396 children with goitre, 112 (28.3%) had evidence of autoimmune thyroiditis (AIT). The median urinary iodine (UI) excretion in the study population as a whole was 14.6 microg/dl. The median UI in the group of children with goiter was 13.3 microg/dl, whereas UI in children with goiter and evidence of AIT was 16.6 microg/dl (p <0.01). Of the 112 children with AIT, 77 (68.7%) were euthyroid, 23 (20.5%) had subclinical hypothyroidism, eight (7.2%) had hypothyroidism and the remaining four (3.6%) had hyperthyroidism. UI was high in goitrous children with AIT, and in children with thyroid dysfunction. Further studies are needed to clarify whether the higher UI in goitrous children with AIT is causally related to AIT or is due to the inability of the diseased thyroid to trap available iodine efficiently.