High thyroid levels refer to the overproduction of the thyroid hormones, T3 (triiodothyronine) and T4 (thyroxine). This condition is also known as hyperthyroidism, and women are about 5 to 10 times more susceptible to develop this condition than men. The thyroid gland is a butterfly-shaped, small organ located in front of the neck. This gland is concerned with the production and secretion of T3 and T4 hormones, which regulate the rate of metabolism.
So, an excess production of these hormones can accelerate the rate of metabolism, or the rate at which food is converted into energy. This in turn, can manifest in several other health problems, as the hormones released by the thyroid gland can affect every part of the body.
The production of thyroid hormones on the other hand, is regulated by the hypothalamus and the pituitary gland. The hypothalamus signals the pituitary gland to produce and secrete the ‘thyroid stimulating hormone’ (TSH). TSH signals the thyroid gland to produce T3 and T4. The amount of TSH released by the pituitary gland depends on the levels of T3 and T4 in blood. So, if the levels of T3 and T4 in blood are high, then the level of TSH will fall.
Normal Thyroid Levels
The normal range for T4 hormone (for adults) is 4.5 – 11.2 mcg/dL
The normal range for T3 hormone (for adults) is 0.1 – 0.2 mcg/dL
The normal value ranges can vary slightly from one laboratory to another, as different laboratories may use different measurements or test different specimens. So, it is better to talk to your physician to evaluate the results of the thyroid test before coming to any conclusion.
It can have several underlying causes, of which Graves’ disease can be considered one of the most common causes. Apart from Graves’ disease, several other factors can cause the levels of thyroid hormones to rise. Some of the most common causes of elevated thyroid levels or hyperthyroidism are explained below.
It is an autoimmune disease, wherein the antibodies produced by the immune system attack the thyroid gland and cause the gland to enlarge. The level of T4 hormone has been found to increase significantly in this disorder. Women, usually those in the age group of 20 to 50 years are more susceptible to develop this condition.
In Graves’ disease, the antibodies produced by the immune system can attack the tissues behind the eyes, along with the thyroid gland. As a result, the eye muscles and tissues can get inflamed, and the eyeball can protrude from the socket. This condition is known as exophthalmos, and this complication can be experienced by a certain percentage of individuals with Graves’ disease.
Scientists have not been able to find out what exactly causes this autoimmune disease, but it has been observed to run in families. So, this disease is presumed to have a genetic predisposition, along with several other triggering factors.
Thyroiditis or the inflammation of the thyroid gland can also cause an overproduction of thyroid hormones. The inflammation can be caused by unknown factors. Sometimes, it can be caused by a viral infection, while at other times, it can be caused by an autoimmune reaction. For example, subacute thyroiditis usually follows a viral infection of the upper respiratory tract, such as mumps and influenza, while Hashimoto’s disease is an autoimmune disorder of the thyroid gland.
Other common types of thyroiditis are, postpartum thyroiditis, silent thyroiditis, and drug-induced thyroiditis. As the name suggests, postpartum thyroiditis occurs after childbirth. This condition can last for about a month or two, followed by a period of hypothyroidism. Eventually, the levels of the thyroid hormones become normal after a few months. Silent thyroiditis is similar to postpartum thyroiditis except for the fact that it is not related to pregnancy or childbirth. The affected individuals develop a small goiter, which is usually not painful.
Sometimes, lumps or nodules can develop on the thyroid gland, and increase the amount of hormones produced by the gland. If hyperthyroidism results due to the development of a single nodule, it is termed as single toxic nodule. On the other hand, if several nodules develop in the thyroid gland, and they cause the excess production of thyroid hormones, the condition is known as toxic multinodular goiter. Thyroid nodules can be benign or malignant, but usually, they are benign or non-cancerous. The nodules can be solid or fluid-filled.
Excessive Intake of Iodine
Iodine is required by the thyroid gland to synthesize thyroid hormones. But its excessive intake can cause thyroid disorders like hyperthyroidism. Kelp or seaweeds contain a very high level of iodine, and so, an excessive intake of kelp and its supplements can raise the risk of developing thyroid disorders.
Thyroid medications that are usually prescribed for the treatment of hypothyroidism can occasionally cause high thyroid levels, especially when they are used for a long time. Drugs like amiodarone used for treating irregular heartbeats can also cause hypo or hyperthyroidism, as this drug is structurally similar to thyroxine.
As mentioned already, thyroid hormones regulate the rate of metabolism and hence, high levels of thyroid hormones raise the rate at which food is converted into energy (metabolism). High levels of thyroid hormones in the body can also affect the nervous system and vital organs like the heart. This condition can manifest in several symptoms, which are enlisted below:
✧ Anxiety and nervousness
✧ Increase in appetite
✧ Unexplained weight loss
✧ Heat intolerance
✧ Palpitations and irregular heartbeat
✧ High blood pressure
✧ Excessive sweating
✧ Excessive thirst
✧ Shortness of breath
✧ Irregular and scanty menstrual flow in women
✧ Muscle weakness
✧ Skin thinning
✧ Changes in bowel patterns (usually an increase in frequency)
✧ An enlarged thyroid or goiter
✧ Hair loss
✧ Brittle and fine hair
✧ Decreased libido
✧ Exophthalmos and red and swollen eyes (if it is caused by Graves’ disease)
✧ Excessive tearing, light sensitivity, and blurred vision (if it is caused by Graves’ disease)
However, people having hyperthyroidism usually do not develop all the symptoms. Most of the affected individuals develop a combination of two or more symptoms, which develop gradually over a period of time.
Diagnosis and Treatment of Hyperthyroidism
A physician usually evaluates the symptoms and medical history of the patient, along with carrying out physical examinations and blood tests, if hyperthyroidism is suspected. Physicians often look for the presence of symptoms like tremors in the fingers, and examine the thyroid gland and the eyes of the patient. However, a confirmed diagnosis requires blood tests to measure the levels of thyroxine (T4) and TSH. A high level of T4, but low level of TSH indicates hyperthyroidism.
If the blood tests show positive results, then two other tests are carried out to determine the underlying causes. These two tests are known as thyroid scan and radioactive iodine uptake test. In radioactive iodine uptake test, a small amount of radioactive iodine is administered. This test measures how much iodine is taken up by the thyroid gland to manufacture thyroid hormones.
After a period of time (usually 2/6/24 hours), the amount of iodine used by the gland is measured. A high uptake indicates hyperthyroidism caused by Graves’ disease or thyroid nodules. But if the thyroid levels are high, and the uptake of radioactive iodine is low, then it is likely to be caused by thyroiditis.
In thyroid scan, a radioactive isotope is injected into the vein present in the hand or inside the elbow. The patient is then asked to lie down with the head stretched backward. A special camera is used in the procedure, which produces images of the thyroid gland.
Hyperthyroidism and its symptoms are treated with radioactive iodine and antithyroid medications like methimazole and propylthiouracil. Beta blockers are usually given for controlling high blood pressure and the heart rate. Radioactive iodine helps shrink the gland, and alleviate the symptoms produced by an overactive thyroid gland.
The antithyroid medications prevent the gland from making excess hormones, and they are usually prescribed for a year or longer. Sometimes, these medications can solve the problem permanently, but at other times, relapses may occur.
Sometimes, surgery is also carried out to remove a large section of the thyroid gland, which however, can give rise to complications, like damage to the vocal cord and parathyroid gland. Therefore, surgery is usually considered only when a patient cannot tolerate antithyroid medications, and cannot have radioactive iodine therapy as well.
High thyroid levels or hyperthyroidism is a bit difficult to diagnose in the early stage. However, most people respond to treatment. If left untreated, this condition can increase the risk of developing heart problems, osteoporosis, and pregnancy complications. Therefore, a physician needs to be consulted, if you experience any of the symptoms of hyperthyroidism persistently for a considerable length of time. This can ensure prompt diagnosis and treatment of the condition, which in turn would help prevent the complications associated with it.