Thyroid disorders in pregnancy: An overview of literature from Pakistan.

Sir,

A study carried out by Elahi et al.,[1] in Lahore, Pakistan revealed that about 79.8% of the pregnant mothers are found to be iodine deficient, out of which 24.7% are moderately deficient in iodine which predisposes the mothers and their neonates to develop iodine deficiency thyroid disorders.

The published editorials in Indian Journal of Endocrinology and Metabolism[23] were absolutely worth reading, as the authors raise such important and unavoidable questions and concerns regarding practices in developing countries possessing limited resources and facilities. India and Pakistan certainly share a spectrum of prevalent diseases which potentially have factors common in their cure and prevention. We are also well-acquainted with the fact that guidelines developed by the western world do not always help us keeping our nations’ yet developing state in view.

An estimated 1-2% of the women in their reproductive age present with thyroid disorders, rendering thyroid disorders being the second most common endocrinological disorders encountered during pregnancy, diabetes being the most common.[4] Thyrotoxicosis during pregnancy, recurrent postpartum thyroiditis, and maternal hypothyroidism are the most common entities encountered during pregnancy and postpartum.[5] The most common cause of maternal hypothyroidism has been found to be autoimmune Hashimoto's thyroiditis in iodine replete areas whereas iodine deficiency is an important cause of goiter in iodine deplete areas.[6]

Since Pakistan is considered an iodine deficient country in the domain plus an iodine deficient Pakistani diet[1] puts the Pakistani population particularly the pregnant mothers on the risk of developing moderate to severe iodine deficiency with maternal hypothyroidism and fetal consequences. But unfortunately we severely lack the local data on the true prevalence of thyroid disorders in pregnancy and their fetal consequences. Pakistan certainly needs a program to mandate iodine supplementation of pregnant mothers and future trials to collect local data for better prevention and treatment practices.

An important question which was raised by the authors in IJEM editorials[23] was if every antenatal patient should be screened for hypothyroidism with thyroid stimulating hormone (TSH) levels since subclinical hypothyroidism is more common than overt hypothyroidism.[5] And yet an even higher percentage of thyroid autoantibody positivity has been observed in pregnant patients.[5] The patients with positive thyroid autoantibody are at higher risk of developing thyroid insufficiency during their pregnancy.[5] In this regard Ghafoor et al.,[7] in Lahore, Pakistan determined the prevalence of thyroid peroxidase (TPO) auto-antibodies among euthyroid pregnant women and its relation with their pregnancy outcome. Surprisingly they found an 11.2% prevalence of positive TPO autoantibodies among euthyroid pregnant mothers. They also recognized significant raised complication rate among TPO auto-antibody positive patients which include high abortion rates and premature birth. The authors, thus not only adjudged raised TPO auto-antibody levels as a good marker of detecting early hypothyroidism but also emphasized its implementation as a screening modality in Pakistan. In other words, state of covert hypothyroidism can be seen in euthyroid patients with TPO auto antibodies positive. Also, treatment of such patients may obviate or reduce the risk of complications, that is, abortions and low birth weight. All the above description thus necessitates the need of revising our practices for the diagnosis and management of thyroid disorders in pregnant patients. Even subclinical hypothyroidism has been significantly found associated with higher rate of miscarriage and preterm delivery, and a lowintelligent quotient (IQ) of the child.[8] This advocates screening of every case at 1st antenatal visit for hypothyroidism and subsequent treatment. Nelson et al.,[9] further warrants subsequent adverse pregnancy outcomes in women previously diagnosed with subclinical hypothyroidism.

Kazi et al.,[10] evaluated the levels of iodine, iron, and selenium in biological samples of Pakistani mothers with goiter and their newly born babies and they found significantly lowered iodine, iron, and selenium levels in the serum and urine samples. With these study results, the authors also suggest the adverse effects of these deficient trace elements on the health of mothers and their newly born infants. A simpler urine iodine excretion screening may thus reveal maternal iodine deficiency and treating it with supplements may preclude severe complications later in pregnancy and in yet unborn fetus. van Mil et al.,[11] further strengthens the adverse health effects on children by evaluating the association between low urinary iodine excretion during early pregnancy and impaired executive functioning in children. The study found an impairment of executive functions in children born to mothers who have had low urinary iodine excretion during early pregnancy. The study assessed the executive functioning of children at 4 years of age and thus, authors suggest further long-term trials to assess if late neuropsychological clinical disorders also develop.

Thyrotoxicosis in pregnancy has found to be associated with fetal anomalies, abortion, preterm labor, and fetal hyperthyroidism with goiter.[5] Shahid[12] found early diagnosis and treatment of hyperthyroid pregnant patients with anti-thyroid drugs and β−blockers associated with improved obstetrical outcome.

Iodine deficiency hypothyroidism seems to be the most important cause of maternal hypothyroidism in our part of the world whereas TPO auto-antibody positivity is yet another concern in our patients having euthyroid clinical status. This demands a revision of our current practices to diagnose and manage the covert cases of thyroid dysfunction in pregnancy to abate adverse obstetrical complications and adverse fetal outcomes. Furthermore, joint research in this regard between India and Pakistan should be fully encouraged as we believe that this would not only bring us an opportunity of frequent sharing of our disease-related knowledge and clinical experiences but also a greater credibility with a wider physicians’ acceptability.