Pharmacology for Nurses Unit 27 Review: Thyroid & Parathyroid Medication

Key Concepts

• Thyroid gland secretes hormones that regulate metabolism, growth, and development
• Parathyroid glands secrete parathyroid hormone (PTH) which regulates calcium levels in the body
• Hypothyroidism occurs when the thyroid gland produces insufficient thyroid hormones
• Hyperthyroidism results from excessive production of thyroid hormones
• Medications used to treat thyroid disorders include levothyroxine, methimazole, and propylthiouracil
• Hyperparathyroidism is characterized by elevated levels of PTH and hypercalcemia
• Hypoparathyroidism is a condition of decreased PTH secretion and hypocalcemia
• Nurses play a crucial role in monitoring patients' response to thyroid and parathyroid medications

Anatomy and Physiology Review

• Thyroid gland is a butterfly-shaped endocrine gland located in the neck
  • Consists of two lobes connected by an isthmus
• Thyroid follicular cells produce and secrete thyroid hormones (T3 and T4)
  • Synthesis of thyroid hormones requires iodine
• Thyroid hormones regulate basal metabolic rate, growth, and development
• Parathyroid glands are four small glands embedded in the posterior surface of the thyroid gland
• Parathyroid glands secrete PTH in response to low serum calcium levels
• PTH increases serum calcium levels by promoting bone resorption, renal calcium reabsorption, and intestinal calcium absorption
• Negative feedback mechanisms regulate the secretion of thyroid hormones and PTH

Types of Thyroid Disorders

• Hypothyroidism is a condition of insufficient thyroid hormone production
  • Causes include autoimmune disorders (Hashimoto's thyroiditis), iodine deficiency, and surgical removal of the thyroid gland
  • Symptoms include fatigue, weight gain, cold intolerance, and dry skin
• Hyperthyroidism is characterized by excessive thyroid hormone production
  • Causes include Graves' disease, toxic multinodular goiter, and thyroiditis
  • Symptoms include weight loss, heat intolerance, palpitations, and anxiety
• Goiter refers to an enlarged thyroid gland, which can be associated with both hypothyroidism and hyperthyroidism
• Thyroid nodules are solid or fluid-filled lumps within the thyroid gland
  • Most thyroid nodules are benign, but some may be malignant (thyroid cancer)
• Thyroiditis is inflammation of the thyroid gland, which can cause transient hyperthyroidism followed by hypothyroidism

Thyroid Medications

• Levothyroxine is a synthetic form of T4 used to treat hypothyroidism
  • Administered orally, typically once daily on an empty stomach
  • Dosage is adjusted based on thyroid function tests (TSH, free T4)
• Methimazole and propylthiouracil (PTU) are antithyroid medications used to treat hyperthyroidism
  • Inhibit the synthesis of thyroid hormones by blocking the enzyme thyroid peroxidase
  • Methimazole is preferred due to a lower risk of hepatotoxicity compared to PTU
• Radioactive iodine (I-131) is used to treat hyperthyroidism and thyroid cancer
  • Concentrated in thyroid cells, causing localized destruction of the gland
• Beta-blockers (propranolol) are used to manage symptomatic hyperthyroidism
  • Alleviate symptoms such as palpitations, tremors, and anxiety

Parathyroid Disorders

• Hyperparathyroidism is a condition of excessive PTH secretion
  • Primary hyperparathyroidism is caused by parathyroid adenomas or hyperplasia
  • Secondary hyperparathyroidism occurs in response to chronic hypocalcemia (renal failure, vitamin D deficiency)
  • Symptoms include bone pain, kidney stones, abdominal pain, and fatigue
• Hypoparathyroidism is characterized by insufficient PTH secretion
  • Causes include surgical removal of parathyroid glands, autoimmune disorders, and genetic mutations
  • Symptoms include muscle cramps, tingling sensations, and seizures due to hypocalcemia
• Pseudohypoparathyroidism is a rare genetic disorder characterized by resistance to PTH
  • Results in hypocalcemia and hyperphosphatemia despite normal or elevated PTH levels

Parathyroid Medications

• Calcium supplements are used to treat hypocalcemia in hypoparathyroidism
  • Administered orally in divided doses to maintain serum calcium levels within the normal range
• Vitamin D analogs (calcitriol) are used in conjunction with calcium supplements to enhance intestinal calcium absorption
  • Calcitriol is the active form of vitamin D and directly stimulates calcium absorption
• Cinacalcet is a calcimimetic medication used to treat secondary hyperparathyroidism in patients with chronic kidney disease
  • Activates calcium-sensing receptors on parathyroid cells, suppressing PTH secretion
• Bisphosphonates (alendronate) may be used to treat bone loss associated with hyperparathyroidism
  • Inhibit bone resorption and increase bone mineral density

Nursing Considerations

• Monitor thyroid function tests (TSH, free T4) regularly in patients taking thyroid medications
  • Assess for signs and symptoms of hypothyroidism or hyperthyroidism
• Educate patients on the importance of taking thyroid medications consistently and at the prescribed times
• Monitor serum calcium and phosphate levels in patients with parathyroid disorders
  • Assess for signs and symptoms of hypocalcemia or hypercalcemia
• Encourage patients with hypoparathyroidism to maintain an adequate intake of calcium and vitamin D through diet and supplements
• Assess patients taking cinacalcet for signs of hypocalcemia (muscle cramps, tingling sensations)
• Collaborate with healthcare providers to adjust medication dosages based on laboratory results and clinical response

Patient Education and Monitoring

• Teach patients about the signs and symptoms of thyroid and parathyroid disorders
  • Emphasize the importance of reporting any new or worsening symptoms to their healthcare provider
• Instruct patients on the proper administration of thyroid and parathyroid medications
  • Levothyroxine should be taken on an empty stomach, at least 30 minutes before breakfast
  • Calcium supplements should be taken in divided doses throughout the day
• Encourage patients to maintain a balanced diet rich in calcium and vitamin D
  • Recommend dietary sources of calcium (dairy products, leafy greens) and vitamin D (fatty fish, fortified foods)
• Advise patients to inform their healthcare provider about any new medications or supplements they are taking
  • Some medications (calcium carbonate, iron supplements) can interfere with the absorption of thyroid hormones
• Emphasize the importance of regular follow-up visits to monitor thyroid and parathyroid function
  • Laboratory tests and clinical assessments help ensure optimal management of thyroid and parathyroid disorders