Thyroid and parathyroid gland diseases and disorders

Hypersecretion and hyposecretion of the hormones from the thyroid and parathyroid glands cause diseases and disorders. The following sections examine thyroid and parathyroid diseases and disorders.

Thyroid diseases

Thyroid diseases cause hypersecretion or hyposecretion of thyroid hormone. Hyperthyroidism and hypothyroidism are described in depth in the following sections.

Hyperthyroidism

Hyperthyroidism occurs when too much thyroid hormone is produced. Hyperthyroidism is more common in women, people with other thyroid conditions, and those over 60 years of age.

The most common cause of hyperthyroidism is Graves disease, and additional causes include thyroid nodules, pituitary disorders and tumors, and thyroiditis. Risk factors include a family history of thyroid disorders and having an existing autoimmune disease. Hyperthyroidism can cause the following conditions:

• Fatigue, muscle weakness, sensitivity to heat, and increased sweating
• More frequent bowel movements and weight loss, even with adequate food intake and an increased appetite
• Difficulty sleeping, restlessness, irritability, nervousness, and anxiety
• Rapid heart rate, irregular heart rate, and palpitations
• Goiter and exophthalmia
• Changes in the menstrual cycle
• Thyrotoxicosis (thyroid storm), a life-threatening condition that causes elevated vital signs (e.g., temperature, pulse, respiration, and blood pressure)

After performing a physical exam, the provider may order thyroid function tests and a radioactive iodine uptake (RAIU) scan. Treatment includes radioactive iodine therapy to shrink the thyroid, antithyroid medication (e.g., methimazole [Tapazole]), and a thyroidectomy.

Hypothyroidism

Hypothyroidism occurs when too little thyroid hormone is produced. Hypothyroidism occurs after thyroidectomy and radiation therapy. Risk factors for hypothyroidism include having a history of an autoimmune disease, a family history of hypothyroidism, or pregnancy in the past 6 months. Another risk factor is being a female over 60 years of age. The signs and symptoms relate to the metabolism slowing down and may include the following:

• Fatigue, muscle weakness, tenderness, aches, and stiffness
• Constipation and weight gain
• Dry skin, sensitivity to cold, and thinning hair
• Slowed heart rate, hoarseness, and depression
• Elevated blood cholesterol

After the provider performs the physical exam, thyroid function tests and a thyroid ultrasound may be done. Treatment requires taking lifelong synthetic thyroid hormone (e.g., levothyroxine [Synthroid]).

Parathyroid diseases

Parathyroid diseases cause hypersecretion or hyposecretion of parathyroid hormone (PTH), which regulates blood calcium levels. Hyperparathyroidism and hypoparathyroidism are described in depth in the following sections.

Hyperparathyroidism

Hyperparathyroidism is a relatively common disorder. It occurs when one or more of the four parathyroid glands over secrete PTH. Hyperparathyroidism causes excessive bone resorption, and the calcium from the bones causes hypercalcemia (abnormally high blood calcium level).

Primary hyperparathyroidism occurs as a result of an adenoma or hyperplasia of one of the four glands, causing an increase in PTH secretion. Secondary hyperparathyroidism occurs with renal disease, which causes hypocalcemia and low vitamin D levels that trigger PTH secretion. The signs and symptoms are related to hypercalcemia and include the following:

• Muscle pain, atrophy, and weakness
• Gastrointestinal pain, nausea, vomiting, and anorexia
• Cardiac arrhythmias, renal calculi, bone tenderness, and fractures

After the physical exam, the provider may order blood tests (e.g., calcium, phosphorus, and PTH by radioimmunoassay) and imaging tests (e.g., x-ray studies, bone density tests). Treatment depends on the cause. Minimally invasive surgery may be done to remove a tumor or gland(s). When hyperplasia occurs, all but half of a gland can be removed. For secondary hyperparathyroidism, the underlying cause is treated. Medications may be prescribed to help increase calcium excretion by the kidneys.

Hypoparathyroidism

Hypoparathyroidism occurs when there is hyposecretion of parathyroid hormone. This reduction of PTH causes hypocalcemia to occur.

Hypoparathyroidism results from injury or damage to the parathyroid glands. Damage and destruction of the glands can result from cancer, radiation, and surgery (e.g., thyroidectomy). The signs and symptoms relate to the hypocalcemia and can include the following:

• Numbness and tingling, spasms, and twitching in the hands and feet
• Confusion and irritability
• Tetany (continuous muscle spasms), laryngospasm, arrhythmias, respiratory paralysis, and death

The provider will perform a physical exam and order blood tests (e.g., calcium, phosphate, and PTH by radioimmunoassay) and an electrocardiogram. Lifelong treatment includes calcium and vitamin D supplements and a high-calcium diet.