Thyroid disorders: prevention and early detection

The word thyroid is derived from the Greek word “thyrus”, which means shield. The thyroid gland produces thyroxine, which is extremely important for the normal functioning of the human body. When thyroid function is normal, this state is known as euthyroid; if low, it is known as hypothyroid and if high, it is called hyperthyroid. 

The swelling of the thyroid gland is a very common occurrence, and a significant percentage of the population will have a thyroid nodule, which may or may not get detected during one’s lifetime.   

How thyroid hormones work 

The thyroid gland mainly produces two hormones: T3 (Tri-iodothyronine) and T4 (Tetraiodothyronine or Thyroxine). Thyroxine or T4 contains four iodine atoms. To exert its effects, T4 is peripherally converted to T3 by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called thyroid stimulating hormone (TSH). The amount of TSH that the pituitary sends into the bloodstream depends on the amount of T4 secreted by the thyroid gland into blood. If the pituitary sees very little T4 in circulating blood, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the bloodstream goes above a certain level, the pituitary’s production of TSH is shut off.  

When to get tested  

If there is too much thyroid hormone or hyperthyroidism, it can cause symptoms such as: increased sweating and feeling hot, feeling like your heart is racing or is beating irregularly, hand tremors, anxiety,  nervousness, and irritability, weight loss, frequent bowel movements or diarrhoea, hair loss, changes in menstrual periods (often lighter and/or less frequent), as well as pain behind the eyes and/or swelling or bulging of eyes.   

When thyroid hormone levels are too low with hypothyroidism, it can cause symptoms such as: dry skin, constipation, depression and forgetfulness, weight gain and increased menstrual flow. 

Thyroid disorders in pregnancy   

After diabetes, thyroid disorders constitute the most common endocrine problems in pregnancy. Hence, women must be well informed and aware about thyroid disorders, their clinical manifestations and their management strategies.  

Thyroid problems in a pregnant woman affect the foetus directly. It is crucial for both the woman and the baby’s health to have normal thyroid function during the entire period of pregnancy and also during the lactation period.  

There are many physiological changes that happen during pregnancy which can mimic thyroid disorders, due to which there may be delays in diagnosing thyroid disorders. There can be either increased or reduced functioning of the thyroid gland. There can be a benign or cancerous nodule developing in the thyroid gland or there can be post-partum thyroiditis.  

During antenatal checkups, all women should be screened, by obtaining a detailed history, a family history, if any, of thyroid disorders, biochemical blood tests (thyroid function tests) and a detailed clinical examination of the neck. Untreated thyroid disorders in a pregnant woman can potentially lead to miscarriages, preterm births, low birth weight babies, a thyroid storm or heart failure.  

Prevention methods include the use iodised salt, exercise, limiting intake of processed food, and avoiding smoking and alcohol intake as well as avoiding any exposure to radiation. If someone is already taking thyroid medication, then in pregnancy, the dose may need adjustments and hence, thyroid function tests are done once a month during the entire course of pregnancy. If someone has a thyroid nodule, then an ultrasound of the neck and fine needle aspiration cytology tests may be done as advised by the treating endocrine physician or surgeon. If a woman has a thyroid nodule while being pregnant, then the treating doctor may decide to plan a surgery either in the second trimester of pregnancy or after she delivers the baby. Hence, consultation with a doctor is a must and every pregnant woman needs to be aware of thyroid disorders. 

Benign thyroid swellings 

There are several causes of benign thyroid swellings. They include: 

Simple goitre: Diffuse hyperplastic, can be physiological as in puberty and pregnancy. Iodine deficiency, Colloid goitre, and ultimately becomes multinodular goitre. 

Dyshormonogenetic goitre: This is due to genetic defects 

Toxic goitre: Diffuse: This is caused by primary Grave’s disease (an autoimmune condition that causes hyperthyroidism) Secondary: multinodular, toxic adenoma. 

Autoimmune thyroiditis and rarely, infections, can also cause benign swellings. 

Presentation and examination 

Patients may notice a swelling over the lower part of neck while looking in the mirror. Close relatives or friends may also notice such a swelling. More often, however, it is incidentally found while doing an ultrasound or CT scan for other indications. 

A clinical history involves finding out: the history of exposure to radiation, family history of thyroid tumours; the patient’s appetite, sleep patterns, weight gain/ loss, intolerance to heat/cold as well as any changes in the voice (hoarseness), difficulties in swallowing, chronic cough, breathing difficulties.    

A clinical examination includes a general examination of the pulse, blood pressure, dry skin, eyes as well as generalised puffiness of face and body. It also includes a local examination of a swelling, if any, in front of the neck that moves up when the patient swallows, as well as feeling for lymph nodes in neck. 

Evaluation and prevention 

Evaluation includes:  

Blood tests: Thyroid Function Tests, TSH, Free T4, Free T3, Thyroid Antibodies [Thyroglobulin, TPO], and an ultrasonography or USG, which is easily available and non-invasive. 

Guided fine needle aspiration cytology (FNAC) of the thyroid and lymph nodes is done to confirm malignant conditions. A TIRADS classification is done by the radiologist to differentiate between benign, suspicious and malignant lesions. 

Prevention measures include the introduction of iodised salt to reduce the incidence of simple goitre and early therapy with thyroxine to regress the initial stages of simple goitre. 

Most patients with multinodular goitre are asymptomatic and do not need operations. They can be followed up by serial ultrasounds. 

When is surgery needed?

Indications of surgery in benign thyroid nodules include: suspicion of malignancy following an FNAC; pressure symptoms, toxicity and cosmetic reasons.  

Surgical options include: hemithyroidectomy, which involves removal of half of the gland and total thyroidectomy, which is complete removal of the gland. 

Malignant lesions  

Cancer of the thyroid: Unlike many other cancers, cancer of the thyroid is one of the cancers that can be cured completely in 90% of patients. 

A thyroid swelling can be asymptomatic. It can be seen as a swelling moving up while swallowing; can present as discomfort in the neck; may be found incidentally on imaging or a patient could present with pain, a change in voice, difficulty in swallowing and difficulty in breathing. 

Malignant lesions are equally common in men and women although thyroid swelling per se are more common in women. 

Risk factors include: age – men above 40 and women above 50 have a higher chance of malignancy; radiation during childhood for neuroblastoma, Wilm’s tumours and lymphoma, iodine deficiency, use of oral contraceptives, obesity, smoking and alcohol consumption.  

Recent weight loss or weight gain, history of radiation exposure, family history of thyroid malignancy, recent increase in size or presence of multiple swellings in the neck are also factors that must be investigated. It can also be part of multiple endocrine neoplasia. 

Thyroid nodules in a child or adolescent should be viewed with suspicion.  

Evaluation includes a good clinical examination. There is usually a unilateral swelling, but it can be bilateral. The evaluation also includes looking for the presence of neck nodes. An ultrasound, FNAC, molecular testing, thyroid function tests, calcium test, ENT examination for vocal cords, a chest x-ray and an anaesthetic assessment may also be part of the evaluation. A multi-disciplinary team is usually involved. 

A carcinoma thyroid can present as a solid thyroid nodule or multinodular goitre 

Common types of thyroid cancer are: papillary carcinoma (about 70-80% of cases); follicular carcinoma; Hurthle cell cancers; medullary carcinoma thyroid; anaplastic; lymphomas and metastatic. 

Treatment 

Carcinoma thyroid, unlike other carcinomas, has excellent prognosis if treated  dequately and early. Treatment paths could include: hemithyroidectomy, which is removing half of the gland, for a very early, less than 1 cm lesion or total thyroidectomy, which is removing both the lobes, with or without lymph node dissection. 

Radioiodine ablation, a treatment that uses radioactive iodine. 

Patients need to be on lifelong thyroid replacement and follow up with TSH and serum thyroglobulin.

What patients should know

Disorders of the thyroid gland, both benign and malignant, are very common. Most thyroid disorders can be detected easily by clinical examination and simple tests with imaging. All thyroid conditions are amenable to proper treatment. Cancer of the thyroid is curable if detected and treated early.  

This article was first published in The Hindu’s e-book Care and Cure. 

(Tushar Yashwant Sonavane is consultant, general endocrine and laparoscopic surgeon, Naruvi Hospitals, Vellore. tushar.s@naruvihospitals.com; Aravindan Nair is consultant, general and endocrine surgeon, Naruvi Hospitals, Vellore. aravindan.n@naruvihospitals.com; Sai Krishna Chaitanya P., is consultant endocrinologist, Naruvi Hospitals, Vellore. saikrishna.p@naruvihospitals.com)