Dr. Shrinath Pratap Shetty, Endocrinologist KMC, hospital Mangalore
The thyroid is one of the classic endocrine glands, which is easily visible and felt compared to other endocrine glands. Endocrine glands are ductless glands which secrete substances called “hormones” directly into the bloodstream. These hormones travel in the bloodstream to reach the target organs where they mediate their action. The thyroid gland produces 2 hormones – T4 and T3 hormones which are involved in various body functions such as energy utilization, weight maintenance, heart rate variability, fertility, menstruation; and finally, brain development and growth in children.
The Thyroid gland is regulated by TSH (thyroid-stimulating hormone) produced by the pituitary gland (also called the master gland). When the T4 /T3 production is not sufficient it is called hypothyroidism. This is characterized by compensatory increase in TSH levels to > 4.5 mIU/ml (range: 0.4-4.5 mIU/ml). Similarly, there is a compensatory decrease in TSH levels when the T4 and T3 hormones are in excess. This picture is characteristic of hyperthyroidism. Since thyroid hormones are an essential part of our body function, both hypothyroidism and hyperthyroidism can have an impact on our health.
A ) Hypothyroidism
Hypothyroidism can be subclinical or overt. In subclinical hypothyroidism, the TSH values are between 4.5-10 mIU/ml with normal T4 and T3 levels. These subjects can wait before starting medicines unless there are specific indicators to start medicines early. However, patients with TSH elevation of >10mIU/ml are candidates for thyroid hormone supplements. About 90% of the patients with hypothyroidism have an autoimmune cause. These subjects have auto-antibodies like anti-TPO antibodies which leads to thyroid gland destruction and subsequently hypothyroidism.
Patients with hypothyroidism can present with weight gain, fatigue, joint pain, increase in sugar values, high cholesterol, menstrual problems and infertility. Even mild hypothyroidism can lead to infertility in an otherwise normal couple. However, not everyone with hypothyroidism is symptomatic. Many of them are incidentally detected during a routine check-up or before elective surgery.
Women of reproductive age who are planning a pregnancy or are already pregnant should optimize their thyroid levels for a better outcome. Subclinical hypothyroidism needs to be treated during pregnancy, which can be stopped after delivery.
Hyperthyroidism is a condition where the thyroid gland is over-functioning leading to an increase in T4 and T3 production which is accompanied by low TSH levels. Graves’ disease is responsible for almost 90% of the cases of hyperthyroidism, it is auto-immune in nature. A similar picture of low TSH, high T4 and T3 is also seen with thyroiditis, where the stored thyroid hormones are released in large quantities prematurely.
During pregnancy, the TSH hormone levels are normally low due to an increase in levels of HCG (human chorionic gonadotropin) which is produced from the placenta. This HCG can stimulate thyroid hormone production during the 1st trimester and lead to a condition called hyperemesis gravidarum. Sometimes a pregnancy may be complicated by hyperthyroidism and the patients may need anti-thyroid drugs depending on the severity. Patients with pre-existing hyperthyroidism need counselling prior to pregnancy since they have a higher risk of abortion and complications.
Some women develop postpartum thyroiditis after delivery, which is again similar to hyperthyroidism but temporary in nature.
Question and Answers
My leg gets swollen recently. Can it be due to thyroid?
Ans. Hypothyroidism can cause fluid retention and leg swelling. However, there are other problems where you can have leg swelling like- renal failure, anaemia, heart failure etc. So, it is important to confirm the diagnosis with a thyroid profile
What are some of the symptoms that mothers should watch out for?
Ans. Mothers should get their TSH checked once the pregnancy is confirmed. Though universal TSH assessment is not part of the present guidelines, they improve pregnancy and foetal outcomes. Unexplained loss of weight, tremors and palpitation during pregnancy can be a feature of gestational thyrotoxicosis/Graves’ disease and needs early evaluation.
Older mothers can have simultaneous thyroid problems and diabetes. What is the relationship between diabetes and thyroid?
Ans. Elderly mothers, especially those with a family history of diabetes can have diabetes
(Gestational diabetes) complicating pregnancy. Such subjects should be screened for thyroid disorders during pregnancy. Treatment of thyroid disorders during pregnancy can improve the pregnancy outcome and result in better sugar control. These medications can be stopped after delivery if diabetes and thyroid problems were mild, to begin with.
If a young mother has thyroid disorder during pregnancy, what are the chances of the baby having the disease at a later stage?
Ans. More than 90 % of the thyroid disorders present during pregnancy are auto-immune in nature, hence the risk of transmission to the baby is very less. However untreated thyroid disorders during pregnancy have a higher risk of complications such as abortion, post-partum haemorrhage and lower IQ score in the child. To avoid undiagnosed congenital hypothyroidism (sporadic) in neonates leading to cretinism, neonatal screening is advised in most centres irrespective of the mother’s health background.
What is a goitre? Should I be concerned about it?
Ans. Any enlargement of the thyroid gland is called goitre. If the goitre has suspicious features of malignancy on the Ultrasound neck and FNA then it should be removed immediately.