Thyroid is one of the most important glands situated in the front or anterior part of the neck. It is the largest endocrine gland which produces hormones. Its purpose is to make, store and release thyroid hormone into the bloodstream. This hormone maintains many important and essential functions of the body i.e. the metabolism of the body. Disorders that affect this butterfly shaped thyroid gland can either speed up or slow down metabolic rate which can lead to a number of symptoms.
The thyroid gland produces T3 and T4 hormones that regulate how the body must use energy. The levels of thyroid hormone are regulated by the pituitary gland, a pea-sized gland in the brain. The pituitary gland makes the thyroid stimulating hormone (TSH), which stimulates the thyroid gland to make thyroid hormone. Over- or under production of any of these three hormones can lead to thyroid diseases.
Thyroid Disease: An Overview
Thyroid disease is a condition which occurs due to either structural or functional problems in the thyroid gland or both.
Structural thyroid problems can be of many types with varied symptoms like enlargement of the thyroid gland (goiter), an atrophic or small thyroid gland, or the development of nodules either single (solitary thyroid nodule) or multiple (multinodular gland) in the thyroid gland.
Functional thyroid problem includes hormonal imbalance which is evaluated with various thyroid function tests. There arises a condition when the gland produces more hormone than the body needs and this condition is called hyperthyroidism. When the gland produces fewer hormones than body needs, it is called hypothyroidism.
Types of Thyroid Disease
The different types of thyroid disease include:
- Hyperthyroidism: A condition where thyroid gland produces more hormone than one's bodily needs. This results in speeding up body's metabolism and heart rate. One of the most common causes of hyperthyroidism is Grave's Disease. Grave's Disease is an immune system disorder wherein the immune system produces antibodies that behave like TSH causing the thyroid gland to produce more thyroid hormones.
- Hypothyroidism: It is an extremely common thyroid disease where there is very less thyroid hormone in the body. In fact, hypothyroidism, many a times, is present for years before it is actually diagnosed and treated. Hypothyroidism can also be related with pregnancy. It can also happen due to autoimmune disorder, thyroid removal, prescription medicines, pituitary disease and iodine deficiency.
- Thyroiditis: This is a type of thyroid disease where there is swelling or inflammation of the thyroid gland. There are several types of thyroiditis: postpartum thyroiditis, subacute thyroiditis, silent thyroiditis, Hashimoto's thyroiditis, acute thyroiditis, drug-induced thyroiditis and radiation-induced thyroiditis. Thyroiditis can cause hypothyroidism, hyperthyroidism or both. For example, with postpartum thyroiditis, patients start having symptoms of hyperthyroidism, followed by symptoms of hypothyroidism post-delivery.
- Goiter: Goiter is a condition of nodular thyroid disease. It is an augmentation of the thyroid (swelling in the neck) that can occur with hypothyroidism or hyperthyroidism and also with benign or malignant (cancerous) nodules. It is mostly caused due to iodine deficiency and is more common in women than in men. Nowadays, with the intake of iodized salt in our daily food habits, goiter is a less common form of thyroid disease.
- Thyroid Nodules: Nodules are abnormal masses or lumps in a body cavity, tissue or organ. Nodules can also develop in thyroid gland. Thyroid nodules occur due to benign tumors, cysts, or rarely due to thyroid cancers. A patient with thyroid nodule will have swelling in one section of the thyroid. This swelled nodule might be filled with fluid or blood or it can be solid. A patient can have one or many thyroid nodule. Thyroid nodules can be benign and may not cause symptoms. In a small group of patients, the thyroid nodule is cancerous.
- Thyroid Cancer: It is one of the most serious forms of thyroid problem. Thyroid cancer is more common with women than men according to National Cancer Institute. It can occur at any age group, but mostly affects to women below 55 years of age. Most common thyroid cancer symptom is swelling or lump in the neck which is usually painless and sometimes it causes difficulty in swallowing of food, sometimes voice might get cracked. Situations worsen if affected person smokes.
Signs and Symptoms of Thyroid Disease
The thyroid disease symptoms vary with the type of disease. Let us see in details the different symptoms of thyroid disease which can also serve as the early warning signs.
- Hyperthyroidism: Patient affected with this type of thyroid disease will notice the symptoms slowly. However over time, overactive thyroid will start increasing body's metabolism causing certain discomforts like:
- Weight loss even if the calorie intake is more than usual
- Eating more than usual
- Feeling nervous or anxious
- Irregular and rapid pulse/heart rate
- Trouble sleeping
- Trembling of hands and fingers
- Increased sweating
- Hot flushes
- Muscle weakness
- Lighter menstrual periods than normal
- Changes in the eyes may include bulging of the eyes, swelling, redness
- It weakens the bone and might cause osteoporosis. Mostly women undergoing menopause are more likely to get affected by osteoporosis.
- Hypothyroidism: Symptoms of hypothyroidism can be mild or severe. People with a mild form of this thyroid disease may not have any symptoms at all. The most life threatening form of hypothyroidism is known as myxedema, which can lead to coma and also death. An underactive thyroid gland can affect all organs and its functions inside the body giving rise to both physical as well as emotional symptoms. Symptoms faced by patients in case of hypothyroidism are as follows:
- Thyroiditis: Thyroiditis will either show symptoms of hyperthyroiditis or hypothyroiditis. Patients frequently feel ill or feverish if they are affected with this type of thyroid disease.
- Goiter: The only visible symptom of goiter is swelling of the thyroid in the neck. If the swelling is more, the visibility is more and it can be clearly felt. Goiter creates problems while breathing, swallowing food, coughing, etc.
- Thyroid Nodule: If thyroid nodule causes more thyroid hormone then it will show symptoms of hyperthyroidism discussed earlier. Sometimes the nodule is large enough which can be felt and seen as inflammation in the neck and at times it can cause problems in swallowing food, breathing or coughing. Thyroid nodule is often non-cancerous.
- Thyroid Cancer: Symptoms of thyroid cancer are:
- Neck pain
- Cracked or hoarse voice
- Enlarged lymph nodes.
Epidemiology of Thyroid Disease
Thyroid disease is mostly found in areas where iodine deficiency is found. Around one third of the world's population lives in areas which has iodine deficiency. In areas where the daily iodine intake goes below 50 μg, goiter is generally endemic; if the RDA of iodine falls below 25 μg congenital hypothyroidism is seen. The prevalence of goiter is 80% high in areas with severe iodine deficiency. Thyroid disease has a prevalence rate of 0.8-5% in any given population and it is about 4-7 times more common in women than men. More than 12% of USA population encounters a thyroid disease in their lifetime. It is estimated that 20 million Americans have some form of thyroid disease.
Prognosis of Thyroid Disease
Most of the thyroid disease is treatable. The type of treatment provided depends on the type of thyroid disease being treated. The prognosis for thyroid disease is good when treated on time. In case of hypothyroidism, medications are to be continued for lifetime. However, if thyroid disease is left untreated, it can lead to serious health complications and can rarely be fatal. Undiagnosed or unattended thyroid disease in pregnant women can increase the risk of miscarriage, premature delivery and can also lead to developmental problems in children.
Causes of Thyroid Disease
The causes of thyroid diseases vary according to the types and are as follows:
- Hyperthyroidism: The reasons that cause hyperthyroidism are:
- Graves' Disease
- Excessive Iodine intake
- Toxic multinodular goiter
- Thyroid nodules which increases the secretion of thyroid hormones.
- Malfunctions of the Pituitary Gland.
- Cancer of the thyroid gland.
- Hypothyroidism: Hypothyroidism is caused due to:
- Resistance to thyroid hormone
- Hashimoto's thyroiditis
- Acute thyroiditis
- Postpartum thyroiditis
- Removal of thyroid gland
- Usage of Lithium drugs.
Complications of Thyroid Disease
Thyroid disease, if attended is highly manageable. A person with a thyroid disease, either hypothyroidism or hyperthyroidism usually needs to take medication for life long. However, if thyroid disease is left untreated it can cause various complications like:
- Untreated hypothyroidism can lead to myxedema coma, a rare but fatal condition.
- Untreated thyroid disease can also lead to swelling of the thyroid gland which can block the airway and thus cause asphyxia. The swelling can be either internal or external.
- Pregnant women with untreated thyroid disease are at an increased risk for miscarriage and premature delivery.
- Children born to mothers with untreated thyroid disease can have severe developmental problems.
- Children with hypothyroidism are at an increased risk of having mental retardation and dwarfism.
- Thyroid disease can also cause problems in conception. It can disrupt the hormonal balance of FSH and LH that are responsible for ovulation. Thyroid disease can also cause lighter or heavy bleeding during menstruation or even irregular periods.
Risk Factors of Thyroid Disease
The risk factors include:
- Reduced or excessive consumption of Iodine
- Genetic history in the family
- Graves' disease
- Hashimoto's thyroiditis
- Thyroid nodules
- Lithium drugs.
Diagnosis of Thyroid Disease
A doctor takes a detailed medical history from the patient and also does physical examination of the neck region based on the symptoms. The following diagnostic tests help in detailed analysis of the condition:
- Blood Tests to Detect Thyroid Disease: Blood tests are done to check the levels of thyroid hormones and TSH. Antibodies against the thyroid tissues may also be diagnosed by blood tests like anti-thyroglobulin, TSH receptor stimulating hormone, or anti-thyroperioxidase.
- Ultrasound to Diagnose Thyroid Disease: The doctor asks for an ultrasound when nodules or enlargement of the thyroid gland is seen. Though nodules of the thyroid gland are not always cancerous; ultrasound helps in differentiating between a benign and malignant nodule. However, ultrasound techniques are not always able to differentiate between benign and malignant cases and hence further tissue biopsy is required.
- Thyroid Disease Diagnosis with Radioiodine Scanning: This scanning technique, also known as radioiodine scintigraphy, helps in determining the shape and activity of the thyroid gland. Radioactive iodine is given to the patient. This radioiodine then goes to the thyroid gland where the radioactive emission helps in taking images to check the shape and function of the thyroid gland before it is excreted through urine.
- Tissue Biopsy for Diagnosing Thyroid Disease: A tissue sample is taken from the thyroid gland with the help of fine needle aspiration for testing under microscope to detect the presence of cancerous cells.
Treatment for Thyroid Disease
The treatment for thyroid disease is as follows:
- Non-Surgical Treatment for Thyroid Disease: Thyroid diseases are highly treatable with non-surgical treatments.
- Levothyroxine is given for hypothyroidism and is usually to be taken for life long to maintain the normal levels of thyroid hormones.
- For people who are sensitive to synthetic thyroid hormones, natural hormones from pigs can be used for maintain the thyroid hormones in the body.
- Thioamide drugs like Carbimazole, Methimazole and Propylthiouracil are used to treat Graves' disease.
- Radioactive iodine is used to treat hyperthyroidism and also thyroid tumors.
- PEI or Percutaneous Ethanol Injections are an alternative treatment method for recurrent thyroid cysts and metastatic thyroid cancer lymph nodes.
- Surgical Treatments for Thyroid Disease: Surgery is often opted in cases of nodules in the thyroid gland, enlargement or thyroid cancer. A nodule or nodules could be removed for biopsy. It can also be done if there is a presence of an adenoma that is functioning autonomously giving rise to hyperthyroidism. Hyperthyroidism due to Graves' disease and also large goiter or the one that presses vital structures in the neck is treated by removing a majority portion of the thyroid gland. A complete thyroidectomy along with removing the associated lymph nodes is performed in case of thyroid cancer. However, this can cause hypothyroidism and hence a person is given thyroid medications to be taken once daily for the rest of the life. In case of thyroid surgery, care must be taken to not affect the parathyroid gland which is situated just behind the thyroid gland and also the recurrent laryngeal nerve. The parathyroid gland helps in maintaining calcium levels in the blood and vitamin D levels in the body; damage to the gland or the blood vessels supplying blood to the gland can lead to sever deficiency of these two vital vitamin and mineral. Laryngeal nerve helps in motor control of the external muscles of larynx; damage to it can paralyze the vocal cord and the related muscles and also change the voice quality.
- Radioiodine Therapy to Treat Thyroid Disease: In cases of large goiter which are non-cancerous, radioiodine therapy is highly effective in stimulating iodine uptake. Radioiodine therapy can also shrink the inflamed gland; however, rarely, it can also cause hypothyroidism.
Prevention of Thyroid Disease
The only way to prevent thyroid disease is to take the daily recommended allowance of Iodine as per WHO is 150mcg for adult women and men, 220mcg for pregnant women and 290mcg for nurturing mothers. The intake chart is as follows:
|RDA for Iodine|
|Birth – 6 months||110 mcg||110 mcg||-||-|
|7 – 12 months||130 mcg||130 mcg||-||-|
|1 – 8 years||90 mcg||90 mcg||-||-|
|9 - 13 years||120 mcg||120 mcg||-||-|
|14 – 18 years||150 mcg||150 mcg||220 mcg||290 mcg|
|19+ years||150 mcg||150 mcg||220 mcg||290 mcg|
Although the daily recommended allowance for pregnant women of 14+ years is 220 mcg, WHO, UNICEF and ICCIDD recommends a daily allowance of 250mcg.
Thyroid disease, although not considered as a major problem, it can be really disturbing as it affects the entire metabolism of the body. It can contribute in sudden increase or decrease in weight. For children, it can lead to mental retardation and dwarfism. For women in the reproductive age, it can cause problems in menstrual cycle, along with problems in conception. Thyroid diseases must be taken seriously and be treated as soon as it is noted to avoid future health complications and rarely it can be fatal.