Hyperthyroidism is a condition in which an overactive thyroid gland produces an excessive amount of thyroid hormones that circulate in the bloodstream. When these thyroid hormones become excess in the body, they can begin to cause problems for you.
The thyroid gland is a butterfly-shaped organ located in the base of your neck; in front of your throat. It is about 2 inches long. The function of the thyroid gland is to release hormones that control your body’s metabolism. Being a part of the endocrine system, your thyroid gland uses iodine from the foods you eat to make two main hormones:
- Triiodothyronine (T3)
- Thyroxine (T4)
The hypothalamus and the pituitary gland in the brain communicate to maintain T3 and T4 balance. These hormones should neither be too high nor too low. To achieve this balance, your hypothalamus produces thyrotropin releasing hormone (TRH) that signals the pituitary gland to produce thyroid stimulating hormone (TSH). The TSH then signals the thyroid gland to produce more or less of T3 and T4 depending on their level in the blood.
- When T3 and T4 levels are low in the blood, the pituitary gland releases more TSH to tell the thyroid gland to produce more thyroid hormones.
- When T3 and T4 levels are high, the pituitary gland releases less TSH to the thyroid gland to slow production of these hormones.
Anyone can have hyperthyroidism, but it is more common in females than males, with a female to male ratio of 5:1. Hence, female sex is a risk factor for hyperthyroidism. In addition, those with family history, particularly of Grave’s disease, are also at risk.
Signs and Symptoms of Hyperthyroidism (Overactive Thyroid)
Common symptoms of hyperthyroidism are as follows:
- Weight loss with increased or normal appetite
- Heat intolerance
- Increased pulse rate
- Irregular heartbeat (arrhythmia)
- Tremor — usually a fine trembling in your hands and fingers
- Changes in menstrual patterns – irregular and scanty periods
- Increased frequency of bowel movements
- An enlarged thyroid gland (goiter)
- Muscle weakness
- Difficulty sleeping
- Skin thinning
- Fine, brittle hair
Causes and Risk Factors
The causes of hyperthyroidism are as follows:
- Graves disease – This is the most common cause of hyperthyroidism. It is an autoimmune disorder in which antibodies are produced and stimulate the thyroid hormones to produce excess thyroid hormones.
- Toxic multi nodular goiter – A multi nodular enlargement of the thyroid gland. It is the second most common cause of hyperthyroidism. These nodules produce excess thyroid hormones.
- Toxic adenoma – A benign solitary nodule in an otherwise non palpable thyroid gland.
- Thyroiditis – Inflammation of the thyroid gland which can occur after a viral infection and sometimes after pregnancy. The inflammation can cause excess thyroid hormones to leak into the bloodstream.
- Drug induced thyroiditis – Drugs like amiodarone or lithium can cause the thyroid gland to produce excess thyroid hormones.
- Excess iodine intake – The thyroid gland uses iodine to make thyroid hormones. An excess of iodine may cause hyperthyroidism. Iodine-induced hyperthyroidism is usually seen in patients who already have an underlying abnormal thyroid gland.
- Excessive intake of thyroid hormones – Taking too much thyroid hormone medication can result in hyperthyroidism.
- Abnormal secretion of thyroid stimulating hormone (TSH) – A tumor in the pituitary gland may cause excessive secretion of TSH which will excessively stimulate the thyroid gland to produce thyroid hormones.
Diagnosis of Hyperthyroidism (Overactive Thyroid)
In making a diagnosis of hyperthyroidism, your doctor will take a full medical history and perform a thorough physical examination. He will be looking out for signs to confirm the suspicion of hyperthyroidism.
To confirm the diagnosis of hyperthyroidism, a blood test known as the thyroid function test will be performed. This blood test measures the level of TSH, T3 and T4. In hyperthyroidism, TSH will be decreased and the thyroid hormones T3 and T4 will be increased.
However, if the hyperthyroidism is due to a TSH secreting pituitary tumor, then the levels of TSH will be increased.
Other investigations to find out why your thyroid is overactive may be done and these include:
- Radioiodine uptake test
- Thyroid scan
- Thyroid ultrasound
How is it Treated?
There are several options your doctor may discuss with you. You are to work with your doctor to make use of the best treatment options available. Treatment options include:
- Antithyroid drugs
- Medications to treat associated symptoms
- Radioactive iodine
Most cases of hyperthyroidism can be treated with only medications. Antithyroid drugs like methimazole and propylthiouracil are examples. They interfere with the production of thyroid hormones. Beta blockers e.g. Propranolol, are also used to manage the rapid heart rate experienced hyperthyroidism. Radioactive iodine is given orally to ablate a hyperactive gland.
In cases where patients do not respond to the therapies above, the thyroid gland may be surgically removed and this is known as thyroidectomy.
Some Complications of Untreated Hyperthyroidism
If you are experiencing any of the symptoms listed above, it is important to see your doctor for proper assessment. Once your doctor is able to diagnose hyperthyroidism, treatment should follow immediately to avoid other complications.
A few of the complications which may arise from hyperthyroidism include:
- Thyroid storm – also known as thyrotoxic crisis is an acute exacerbation of hyperthyroidism. It is a life-threatening condition.
- Arrhythmia – an abnormal heart beat.
- Sudden cardiac arrest.
- Brittle bones – excessive thyroid hormones interferes with your body’s ability to incorporate calcium into your bones.
- Eye problems – bulging eyes, blurred or double vision.
- Endocrineweb – Thyroid gland overview
- Medicinenet – Hyperthyroidism
- Amboss – hyperthyroidism
- Medscape – Hyperthyroidism
- Mayo Clinic – Hyperthyroidism