Thyroid: Types of disorders due to imbalance in thyroid hormones, risk factors, symptoms, protocol for testing
Here's all you need to know about thyroid hormones in normal health and disease conditions, the types of disorders due to imbalance in thyroid hormones, their symptoms and protocol for testing of thyroid diseases
The thyroid gland, located in the front of the neck, is the main source of thyroid hormones in the body and hypothalamic thyrotropin-releasing hormone (TRH) stimulates thyroid-stimulating hormone (TSH) synthesis from pituitary gland of our body. TSH stimulates thyroid hormone (T3,T4) synthesis with the help of thyroid peroxidase (TPO) enzyme from thyroglobulin protein and iodine within the gland.
Very minute amount of total thyroid hormones is not bound to any proteins in the circulation and known as free thyroid hormones, which are responsible for the biological activities within the body. For the uninitiated, thyroid hormones maintains key functions such as metabolism rate in body, heart functions, digestive functions, muscle health, brain development, bone health etc.
Disorders due to imbalance in thyroid hormones
In an interview with HT Lifestyle, Dr Soumi Ghosh, Consultant Biochemist at Neuberg Anand Reference Laboratory, highlighted two types of thyroid disorders and their symptoms as:
1.Hypothyroidism- It is associated with decreased free and total thyroid hormones and increased or decreased TSH according to the causative factors. Subclinical hypothyroidism is a condition where persistent elevation in TSH (6 to 12 weeks or longer) is seen but FT4concentrations is found within the normal range.
Among the varieties of hypothyroidism, congenital hypothyroidism (presence since birth) is the most important, as it requires an early diagnosis and treatment to prevent brain damage. Maternal hypothyroidism is a risk factor for developing this disease. Other causes of hypothyroidism are antibodies developed in a person against his or her own thyroid gland, bacterial or viral inflammation in the thyroid glands leading to its damage, radiation or surgery in the thyroid glands. Apart from that certain foods (for example cabbage, cauliflower, soy products, peaches, peanuts) and certain drugs can interfere with thyroid hormone synthesis and cause hypothyroidism.
Risk factors for hypothyroidism include advancing age, type 1 diabetes, family history of thyroid disease, goitre, previous hyperthyroidism, external-beam radiation in the head and neck area, baby born with Down syndrome and females are more prone to develop thyroid disease.
Clinical symptoms suggestive of hypothyroidism include mental dullness, increased sleeping, lethargy, deepening of the voice, hair loss, weight gain, cold intolerance, menstrual irregularities, infertility, growth failure, delayed puberty in adolescents, constipation, muscle weakness or cramps, depression. Physical signs in hypothyroidism include decreased heart rate and blood pressure, cool and dry skin, puffy eyes, loss of eyebrows, delayed muscle reflexes, radiologic evidence of delayed bone age in children. In cases of severe hypothyroidism, congestive heart failure or coma may develop. In children with untreated congenital hypothyroidism, severe growth failure and mental retardation ensue.
2.Hyperthyroidism- This results from increased free and total thyroid hormones and decreased hormonal or increased TSH in the body as per the causative factors.
The causes are autoimmune thyroid disease like Graves’ disease, viral or bacterial infections of thyroid gland lead to release of more thyroid hormones, overproduction of thyroid hormones due to certain unknown causes and over consumption of Iodine etc. Risk factors for hyperthyroidism include advancing age, personal or family history of thyroid diseases, and intake of iodine-containing drugs, like amiodarone, and females are more prone to develop thyroid disease.
Symptoms include nervousness, emotional liability, restlessness, sleeplessness, difficulty in concentrating, smooth and/or shiny hair and skin, weight loss, excessive sweating, heat intolerance, menstrual irregularities, diarrhoea etc. Physical signs are increased heart rate, irregular heartbeats, increased blood pressure, warm and damp skin, tremor, signs of ophthalmopathy (changes in the eye). Euthyroid hyperthyroxinemia is a condition where total T4 is increased but TSH, free thyroid hormones and total T3 are normal. This is usually seen in nonthyroidal illness and abnormalities in thyroid hormone binding proteins.
Why thyroid diseases are common in the communities?
Dr Soumi Ghosh revealed, “There is often a delay in the diagnosis and management of hypothyroidism mainly due to the lack of awareness in the population as well as the lack of facilities for screening program specially in newborns and blood testing in others. Early detection is the most important to prevent lots of physiological variations leading to complications.”
Protocol for testing of thyroid diseases
According to Dr Soumi Ghosh, for any kind of suspected hypothyroidism or hyperthyroidism blood tests like TSH, free or total thyroid hormones should be tested. He said, “Additionally, antibody to thyroid peroxidase (TPO), thyroglobulin and antibody to thyroglobulin are needed to be tested in case of autoimmune disorders, thyroid gland inflammation or malignancy, thyroid surgery or radiation treatment. Thyroid scan and uptake of radioactive Iodine measurement are used in certain cases.”
Sharing that as a laboratory professional, they have seen many cases of variation in TSH levels in the same person from day to day and even at different times of a same day based on body’s metabolic requirement for thyroid hormones, Dr Soumi Ghosh said, “In some cases variation can be as much as 50% or beyond that. With a slight change in concentration of free thyroid hormones, TSH concentration can be changed rapidly and drastically. Any stress, inflammation, infection, strenuous physical activity, surgery can alter the TSH levels.”
She advised, “Test TSH always in a healthy condition so that you can have a reference of individual’s basal levels. It should be kept in mind that there is a diurnal variation of TSH secretion, with peak values after midnight and early morning and drop in the afternoon. It should be tested in the fasting early morning sample and also at the same time of the day in case of serial monitoring of the TSH levels. A borderline abnormal value should always be repeated within a week or so to be certain that it is representative."
She added, “A minimally suitable TSH assay should be able to quantitate concentrations of TSH as small as 0.1 mIU/L or lower than that. Screening for thyroid dysfunction can be advised to newborns, non-pregnant women of reproductive age group, asymptomatic adults. The primary screening test for thyroid dysfunction is serum TSH followed by other tests over 3 to 6 months to confirm or rule out abnormal findings.”