Thyroid disorders are conditions that affect the thyroid gland, a butterfly-shaped gland in the front of the neck. The thyroid has important roles to regulate numerous metabolic processes throughout the body. Different types of thyroid disorders affect either its structure or function.
The thyroid gland is located below the Adam's apple wrapped around the trachea (windpipe). A thin area of tissue in the gland's middle, known as the isthmus, joins the two thyroid lobes on each side. The thyroid uses iodine to produce vital hormones. Thyroxine, also known as T4, is the primary hormone produced by the gland. After delivery via the bloodstream to the body's tissues, a small portion of the T4 released from the gland is converted to triiodothyronine (T3), which is the most active hormone.
The function of the thyroid gland is regulated by a feedback mechanism involving the brain. When thyroid hormone levels are low, the hypothalamus in the brain produces a hormone known as thyrotropin-releasing hormone (TRH) that causes the pituitary gland (located at the base of the brain) to release thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to release more T4.
Since the thyroid gland is controlled by the pituitary gland and hypothalamus, disorders of these tissues can also affect thyroid function and cause thyroid problems.
What are the specific kinds of thyroid disorders?
Hypothyroidism results from the thyroid gland producing an insufficient amount of thyroid hormone. It can develop from problems within the thyroid gland, pituitary gland, or hypothalamus. Symptoms of hypothyroidism can include:
2. Poor concentration or feeling mentally foggy
3. Dry skin
5. Feeling cold
6. Fluid retention
7. Muscle and joint aches
9. Prolonged or excessive menstrual bleeding in women
Some common causes of hypothyroidism include:
1. Hashimoto's thyroiditis (an autoimmune condition that causes inflammation of the thyroid gland)
2. Thyroid hormone resistance
3. Other types of thyroiditis (inflammation of the thyroid), such as acute thyroiditis and postpartum thyroiditis
Hyperthyroidism describes excessive production of thyroid hormone, a less common condition than hypothyroidism. Symptoms of hypothyroidism usually relate to increased metabolism. In mild cases, there may not be apparent symptoms. Symptoms and signs of hyperthyroidism can include:
3. Fast heart rate
5. Intolerance for heat
6. Increase in bowel movements
7. Increased sweating
8. Concentration problems
9. Unintentional weight loss
Some of the most common causes of hyperthyroidism are:
1. Graves disease
2. Toxic multinodular goitre
3. Thyroid nodules that overexpress thyroid hormone
4. Excessive iodine consumption
A goitre simply describes an enlargement of the thyroid gland, regardless of cause. A goitre is not a specific disease per se. A goitre may be associated with hypothyroidism, hyperthyroidism, or normal thyroid function.
Nodules are lumps or abnormal masses within the thyroid. Nodules can be caused by benign cysts, benign tumours, or, less commonly, by cancers of the thyroid. Nodules may be single or multiple and can vary in size. If nodules are excessively large, they may cause symptoms related to compression of nearby structures.
Thyroid cancer is far more common among adult women than men or youth. About 2/3 of cases occur in people under age 55. There are different kinds of thyroid cancer, depending upon the specific cell type within the thyroid that has become cancerous. Most cases of thyroid cancer have a good prognosis and high survival rates, especially when diagnosed in its early stages.
What is the outlook for thyroid disorders?
In most cases, thyroid disorders can be well managed with medical treatment and are not life-threatening. Some conditions may require surgery. The outlook for most people with thyroid cancer is also good, although patients with thyroid cancer that has spread throughout the body have a poorer prognosis. Therefore, as always, regular checkups are a lifesaver.