Thyroid disorders and pregnancy

As your pregnancy advances, you may experience tiredness like you have never experienced before, or you might feel somewhat lethargic and nauseated - all normal signs of a blissfully pregnant mum, you have been told.

While this is true, expectant mothers should also be careful to note that thyroid problems can produce symptoms which are so similar to those of pregnancy that they go unrecognised.

Regrettably, many women are not aware that thyroid problems can develop with pregnancy, let alone watch out for the warning signs. A normal pregnancy results in a number of important physiological and hormonal changes before, during and after pregnancy (postpartum) that can alter the thyroid function, even in women with no thyroid abnormalities.

In fact, approximately 10 per cent of all women suffer from thyroid dysfunction in the first year after pregnancy.

Thyroid woes

The thyroid gland is a small butterfly shaped organ located in front of the windpipe in the neck area. It regulates the production of thyroid hormones which in turn regulates many of the body's functions, including those connected with metabolism and fertility.

Thyroid disorders are relatively common. More than 200 million people worldwide have problems with their thyroid, with more than half of them actually unaware of their condition. Unfortunately, women are eight times more susceptible to the disease than men. Thyroid disorders can affect women during their key life progressions, from puberty to menopause.

Thyroid disorders may have different causes, such as an autoimmune disease or nodule formation within the gland. Whether too little or too much thyroid hormone is produced can have far-reaching effects because many of the processes in the body are controlled by thyroid hormones.

Hypothyroidism, a condition when too little thyroid hormones are produced, is the most common thyroid disorder after childbirth. On the flipside, maternal hyperthyroidism during pregnancy is most commonly caused by Graves' disease, which occurs in 1 in 1500 pregnant patients.

Graves' disease is an autoimmune disorder in which the body's defense system attacks the thyroid gland, resulting in too much thyroid hormone released.

Thyroid disorders and pregnancy

Thyroid disorders and pregnancy

While some women may actually have an existing thyroid disorder before pregnancy, others may develop thyroid problems for the first time during pregnancy. There are also others who develop thyroid disorders after giving birth. Women may develop thyroid problems at any point up to a year after childbirth.

As the need for iodine increases during pregnancy and breastfeeding, the most common cause of maternal thyroid gland enlargement in pregnancy on the global scale is insufficient iodine in the diet. Based on the World Health Organization's recommendation, iodine intake of 200 micrograms/day is required during pregnancy to maintain adequate thyroid hormone production. Fortunately, this is not a problem in our local population as we generally have high levels of dietary iodine intake.

If thyroid dysfunction in a pregnancy goes untreated, it can have adverse effects on the fetus and the mother's well-being. The harmful effects of thyroid dysfunction can also affect the development in the early life of the child.

The baby is completely dependent on the mother for the production of thyroid hormone during the first 10-12 weeks of pregnancy. By the end of the first trimester, the baby's thyroid begins to produce thyroid hormone on its own; however, the baby remains dependent on the mother for ingestion of adequate amounts of iodine, which is essential to make the thyroid hormones.

Going untreated

Leaving thyroid problems untreated can pose problems to the pregnancy.

Hypothyroidism, for example, can increase the risk of miscarriage by causing the placenta to separate from the inner wall of the uterus before the baby is born. This is a condition known as placental abruption, which can be life threatening to both mother and baby. The mother is also at an increased risk of pregnancy-induced hypertension and pre-eclampsia. The baby is also at risk of premature birth or being born with a low birth weight.

During pregnancy, hyperthyroidism increases the risk for spontaneous abortion and maternal heart failure. Hyperthyroidism also carries a high risk for the baby such as increased incidence of stillbirth, preterm delivery and intrauterine growth retardation.

Going unnoticed

The sooner thyroid problems are detected and treated; the more effectively it can be managed, allowing mothers-to-be to seek the appropriate treatment to control the potentially high risk conditions that can harm both the mother and baby.

Expectant mothers need to be on alert for symptoms. Signs of hyperthyroidism include faster than normal heart rates (tachyacardia), nervousness, tremors, heat intolerance, weight loss, frequent stools, excessive sweating, palpitation, and hypertension. More obvious signs would include goiter, in which case the enlargement of the thyroid gland appears as a swelling in front of the neck.

In hypothyroidism, relatively mild symptoms include modest weight gain, lethargy, decrease in exercise capacity and intolerance to cold. More prominent symptoms will include constipation, hoarseness, hair loss, brittle nails, dry skin and development of a goiter.

More often than not, many women or even doctors may overlook the symptoms and not suspect thyroid disorders as the root of the problem. The symptoms of thyroid problems are so similar to that of pregnancy that the correct diagnosis of thyroid disorder can be easily missed, depending on the degree of severity of the disorder. If something does not feel right, women should alert their doctor and be tested to rule out thyroid disorders.

New mothers should remember to get follow up medical attention even after delivery, as the thyroid condition does not usually resolve itself and varied therapy may be required to be continued as necessary. If new mothers are intending to breastfeed, fret not as the medications used are usually safe for nursing mothers and their babies.

This article was contributed by Dr Loh Keh Chuan. Dr Loh is a senior consultant endocrinologist at Mount Elizabeth Medical Centre.