The thyroid gland produces the thyroxine hormone that regulates metabolism (energy release and levels), and acts like a vehicle’s accelerator. The thyroid is a small butterfly shaped, hormone producing (endocrine) gland in the front of the neck, wrapped around the breathing tube (Trachea), inbetween vital structures like the Jugular and Carotid vessels, swallowing tube (Esophagus), the voice box (Larynx) and its nerves, and the calcium controlling parathyroid glands. Swelling of the thyroid is called goitre. Thyroid disorders or diseases can affect anyone at any age and are so common that May 25th is observed as World Thyroid Day to raise awareness about thyroid diseases and the importance of early detection and treatment. This day coincides with the anniversary of the European Thyroid Association, which initially spearheaded public education about the importance of thyroid health and the impact of thyroid diseases. Women are 5 to 8 times more likely than men to experience thyroid disorders. One in eight women develops a thyroid disorder, especially hypothyroidism, due to autoimmune thyroiditis. Thyroid diseases may be diet-related (deficiency of Iodine, excess of Iodine blockers) or genetic. Thyroid function and body weight are closely related, each influencing the other.
IODINE AND THYROID: Iodine is essential for thyroid hormone production, and its deficiency is especially seen in hilly and iodine-poor soil regions, and those consuming excessive amounts of goitre-producing (goitrogens), plant-protecting toxins. Brassica (also called Cruciferous) vegetables like cauliflower, cabbage, kohlrabi (knol khol), broccoli, Brussels sprouts, turnip, mustard, kale, and canola/rapeseed oil contain Glucosinolates, which are responsible for plant protection and the pungent flavours. Glucosinolates in Brassica vegetables and cyanogenic glycosides in Cassava, if not removed by adequate boiling, will be converted to thiocyanates during digestion, which interfere with iodine absorption by the thyroid. Iodine deficiency retards growth of foetus and children, causes multinodular goitre (thyroid swellings) later in life. Severe iodine deficiency during pregnancy can lead to stillbirth, spontaneous abortion, and congenital abnormalities like cretinism, a severe form of mental retardation. Seafood, dairy products, iodized salt, and some fortified foods are good sources of Iodine. Pregnant or breastfeeding women may be advised to take an iodine supplement. Excessive iodine intake can be harmful. In Japan, “iodine goitre” occurs in children and adults who consume large amounts of iodine from seaweed..
HYPOTHYROIDISM OR UNDERACTIVE THYROID: Hypothyroidism in children leads to intellectual impairment and growth retardation. Symptoms of inadequate thyroid hormone levels include fatigue, weight gain despite poor appetite, sensitivity to cold, dry thick skin, puffy face, constipation, joint and muscle aches and stiffness, thinning dry, brittle hair, hair loss, heavy or irregular menstrual periods in women, hoarse voice, mood changes like depression, forgetfulness, and difficulty concentrating. The commonest cause of hypothyroidism is Hashimoto’s autoimmune thyroiditis (inflammation of the thyroid gland), where the immune system mistakenly attacks the thyroid gland. It can present with neck pain, excess release of thyroxine from the damaged thyroid with transient hyperthyroid symptoms, followed later by hypothyroidism. Hypothyroidism after pregnancy (postpartum thyroiditis) is similar but usually temporary. Hypothyroidism is less often due to iodine deficiency, surgical removal of the thyroid without adequate medication, radiation treatment of head and neck cancers, damage to the thyroid due to diseases or cancer, and certain medications like Lithium used for certain psychiatric disorders. Congenital causes include absent or wrongly located thyroid, hereditary defects in thyroid hormone synthesis mechanism, and genetic mutations in the thyroid-stimulating hormone (TSH) receptor sites in the thyroid gland. Rarely, problems with the pituitary gland, the master endocrine gland, which regulates all hormones, can cause secondary hypothyroidism. Hypothyroidism is treated with levothyroxine (T4), a substitute for the thyroid hormone, whose dosage is determined and monitored by checking the TSH level. In some cases, liothyronine (T3) may also be required.
HYPERTHYROIDISM OR OVERACTIVE THYROID: Excessive thyroxine release either by an overstimulated overactive thyroid, or a damaged thyroid, presents with symptoms of rapid heartbeat, palpitations, weight loss despite increased appetite, diarrhoea, nervousness, anxiety, insomnia, fatigue, tremors, heat intolerance, increased sweating, lighter or missed periods in women, brittle hair, hair loss, goitre, osteoporosis, and in Graves’ disease bulging eyes (exophthalmos). In children, hyperthyroidism causes cognitive delays and can be life-threatening in newborns. The commonest cause of hyperthyroidism is Graves’ disease, an autoimmune disorder, where the immune system produces antibodies that overstimulate the thyroid gland. As mentioned earlier, Hashimoto’s thyroiditis initially presents as hyperthyroidism due to the excess release of stored thyroxine. Lumps or nodules within the thyroid gland can sometimes become overactive. Excess Iodine consumption through dietary sources or certain medications and overdose of levothyroxine can lead to hyperthyroidism. Rare, benign tumours of the pituitary gland can overstimulate the thyroid. High levels of human chorionic gonadotrophin (hCG), structurally similar to TSH, can overstimulate the thyroid gland in early pregnancy, multiple pregnancies, molar pregnancies, or trophoblastic tumours. Treatment depends on the cause of hyperthyroidism.
THYROID PROBLEMS IN PREGNANT WOMEN: Thyroid problems in pregnant women can lead to serious complications, even death of the mother and the baby. During pregnancy, untreated hypothyroidism or uncontrolled hyperthyroidism can lead to maternal muscle pain and weakness, gestational (during pregnancy) diabetes, anaemia and serious complications like heavy vaginal bleeding with foetal distress (placental abruption), bleeding after delivery (postpartum haemorrhage), hypertensive disorders of pregnancy (HDP), and heart failure. HDP includes preeclampsia (hypertension with protein leak in urine beyond 20 weeks of pregnancy), gestational hypertension, and their combined variants. HDPs are a leading cause of maternal and perinatal morbidity and mortality, with a significant impact on long-term cardiovascular health. Risk factors include diabetes, obesity, chronic kidney disease, and HDP during previous pregnancy. Thyroid storm, a sudden, severe worsening of hyperthyroidism, can be life-threatening. Foetal complications include miscarriage, premature birth, low birth weight, stillbirth, and developmental delays as the child relies on maternal thyroid hormones. Screening of women of reproductive age; early recognition and treatment of thyroid disorders during pregnancy are crucial for the mother and baby. TSH levels and blood pressure are routinely checked throughout pregnancy, and the treatment is adjusted.
THYROID SWELLINGS (GOITRE): Thyroid swelling can be a solitary benign or malignant (cancer) nodule in any part of the gland, or multiple nodules in the gland (Multinodular goitre), or an uneven or uniform enlargement of the whole gland. A mild uniform enlargement due to hypothyroidism is treated with levothyroxine. In Graves’ disease, goitre is treated initially with thyroid blocking drugs, followed by radioactive Iodine (RAI) ablation or surgery. RAI ablation is effective in treating hyperactive solitary thyroid nodules. Benign small thyroid swellings are investigated and are followed up if slow-growing. A suspicious or rapidly growing nodule is surgically removed with half of the thyroid and biopsied. A growing multinodular goitre, usually due to iodine deficiency in childhood, is surgically removed as it presses on the windpipe, swallowing tube, and nerves, causing breathing and swallowing problems, hoarseness or a change in voice, and neck pain. Hyperthyroidism can develop with Iodine supplementation in individuals who have been iodine-deficient for a long time; hence, their multinodular goitres are treated with surgery and not with Iodine. Thyroid cancer is treated with surgical removal of the thyroid gland and any spread locally. Surgical removal of the thyroid is followed by RAI ablation of any cancer residue or spread, and by levothyroxine and calcium supplements for life.
Thyroid surgery is traditionally performed through a lower neck incision, which leaves a visible scar. Endoscopic (laparoscopic is a misnomer in the neck) and robotic surgery through multiple small cuts were introduced for cosmetic reasons. One of these cuts has to be enlarged to remove the thyroid swelling, or the thyroid has to be cut up and squeezed through these cuts, adversely affecting the quality of biopsy reports. Hence, more than 15 years ago, this author developed a technique of thyroid surgery through an incision high in the neck, where the scar, hidden by the jaw, is not seen. Even massive goitres can be removed intact and safely by this technique. External radiation therapy and chemotherapy are not used for most thyroid cancers. Thyroid cancers are usually of the papillary variety and have excellent cure rates if treated early.
The thyroid is a vital hormone-secreting organ that controls metabolism. It is important to be aware of thyroid problems, their symptoms, and to seek medical advice early, especially in pregnant women and children, to avoid grave consequences. Most thyroid cancers can be cured with surgery and RAI, if detected early.
Dr. P.S.Venkatesh Rao is a Consultant Endocrine, Breast & Laparoscopic Surgeon, Bengaluru.