Anatomy and Physiology
The parathyroid glands, of which there are usually four (one on each “wing” of the thyroid glands) are embedded on the posterior aspect of the thyroid glands. They are responsible for the production of parathormones, the parathyroid hormones responsible for regulating calcium and phosphorus metabolism.
- Increased parathormone results in increased calcium absorption from the kidney, GI, and bones. It also tends to lower the blood phosphorus level. Some actions of parathormone are strengthened by vitamin D.
- Parathormone is regulated by a negative feedback system, where increased serum calcium inhibits parathormone production.
Hyperparathyroidism
Overproduction of parathormone, characterized by ==bone decalcification and the development of calcium-containing renal calculi==.
- Primary hyperparathyroidism occurs two to four times more often in women than in men.
- Most commonly found in people between 60 and 70 years of age, and is rare in children younger than 15 years of age; a 10-fold increase from 15 to 65 years of age.
- Incidence is ~25 in 100,000, but only about half of them are symptomatic.
- Secondary hyperparathyroidism is similar to the primary form, and occurs in patients with chronic renal failure and “renal rickets” as a result of phosphorus retention. Phosphorus stimulates the parathyroid glands, and parathormone is oversecreted.
Assessment Findings
- Most symptomatic findings are related to hypercalcemia: apathy, fatigue, muscle weakness, nausea, vomiting, constipation, hypertension, and cardiac dysrhythmias may occur.
- Psychological effects vary from irritability, neurosis, to psychoses due to the calcium’s direct effect on the brain and nervous system; ==increased calcium decreases the excitation potential of nerve and muscle tissue==.
- An important complication of hyperparathyroidism is the formation and excretion of renal calculi from renal excretion of calcium and phosphorus. This occurs in 55% of patients with primary hyperparathyroidism.
- Calcium phosphate precipitation in the renal pelvis and parenchyma results in renal calculi, obstruction, pyelonephritis, and renal failure.
- Musculoskeletal symptoms that accompany hyperparathyroidism may be caused by the demineralization of the bones or through benign giant cells from osteoclast overgrowth.
- Skeletal pain and tenderness may occur, especially at the back and joints. Weight-bearing results in pain, pathologic fractures form, bone deformities, and stature shortening may occur.
- Gastrointestinal symptoms may be mostly caused by incidence of peptic ulcers and pancreatitis found in hyperparathyroidism.
Diagnostic Examination
- Diagnosed through persistent elevation of serum calcium levels and parathormone concentration.
- Parathormone Radioimmunoassays are sensitive and differentiate primary hyperparathyroidism with other causes of hypercalcemia.
- Bone scans or x-rays are used in advanced disease to determine bone changes.
- Double-antibody Parathyroid Hormone Test is used to differentiate primary hyperparathyroidism and malignancy as a cause of hypercalcemia.
- Imaging Studies and others e.g. UTZ, MRI, Thallium Scan, and Fine-needle Biopsy can evaluate the function of the parathyroids and localize parathyroid cysts, adenomas, or hyperplasia.
Medical Management
- Surgical Management: removal of abnormal parathyroid tissue with minimally invasive parathyroidectomy techniques performed on an outpatient basis. This may not be required for asymptomatic patients, but they should be monitored for development of symptoms and formation of renal calculi.
- Asymptomatic patients may still qualify for surgery if they are (1) <50 years old, (2) unlikely to participate in follow-up care, (3) >1.0 mg/dL serum calcium, (4) urinary calcium is >400 mg/day, (5) exhibit a 30% or greater decreases in renal function, and (6) complains of (primary hyperparathyroidism) nephrocalcinosis, osteoporosis, or severe psychoneurologic disorders. These criteria, however, has been considered conservative by many authors.
- Hydration Therapy: a daily fluid intake of 2,000 mL or more is encouraged to help prevent calculus formation.
- Cranberry Juice can be recommended as it lowers urine pH. It may also be added to other juices or to ginger ale for variety. Cranberry extract tablets may also be used.
- Instruct the patient to report any manifestations of renal calculi, such as abdominal pain and hematuria.
- Mobility: Walking or using a rocking chair (for those with limited mobility) is encouraged as bones that are subjected to regular stress will retain more calcium. Bed rest increases calcium excretion and the subsequent risk for renal calculi.
- Oral phosphates may lower calcium levels, but is not used for long-term therapy due to the risk for ectopic calcium phosphate deposition in soft tissues.
- Diet and Medications: Make to sure to meet nutritional needs, but avoid restriction or excess calcium
Nursing Management
Management is the same as patients undergoing thyroidectomy, with precautions for airway patency, dehydration, immobility, and diet being important both pre- and post-operatively. Monitor for tetany, a symptom of calcium-phosphorus imbalance. Compensation of the remaining parathyroid tissue to reach homeostasis is often quick, and only mild, transient postoperative hypocalcemia occurs. Ensure the patient understands the importance of follow-up care for monitoring these serum levels.
An Acute Hypercalcemic Crisis is the main complication of hyperparathyroidism, where an extreme elevation of serum calcium levels greater than 15 mg/dL (3.7 mmol/L) occurs. Neurologic, Cardiovascular, and Renal symptoms occur and may be life-threatening. Treatment includes:
- Rehydration with large volumes of IV fluids
- Diuretic agents to promote renal excretion of excess calcium
- Phosphate therapy to correct hypophosphatemia, and promote deposition of calcium into bone as well as reducing GI absorption of calcium.
- Cytotoxic agents (e.g. mithramycin), calcitonin, and dialysis may be used to decrease serum calcium levels quickly in emergency situations.
- Calcitonin and Corticosteroids have been used for emergencies to increase calcium deposition, as well as Bisphophonates e.g. Etidronate (Didronel), Pamidronate (Aredia).
Hypoparathyroidism
Most commonly caused by inadequacy following surgery or interruption of the blood supply to the parathyroid glands.