Parathyroid Disorders

Anatomy and Physiology of the Parathyroid Glands

The parathyroid glands are four small, yellowish-brown, pea-sized endocrine glands located on the posterior surface of the thyroid gland. Typically, two lie superiorly and two inferiorly. Their primary hormone, parathyroid hormone (PTH), acts directly on bones, kidneys, and the intestines to maintain serum calcium within the tight physiological range of 8.5 to 10.2 mg/dL. When circulating calcium levels drop, parathyroid cells release stored PTH to restore balance.

Pathophysiology and Calcium Homeostasis

Calcium homeostasis relies on a delicate feedback loop involving PTH, calcitonin, and active vitamin D (calcitriol). PTH raises serum calcium through three distinct mechanisms:

• Bone resorption: Stimulates osteoclast activity to release calcium and phosphate from the bone matrix into the bloodstream.
• Renal tubular reabsorption: Increases calcium reabsorption in the distal tubules while promoting the excretion of phosphate.
• Intestinal absorption: Enhances calcium absorption in the gut by stimulating the kidneys to convert inactive vitamin D into its active form.

Phosphate and calcium have an inverse relationship in the blood; when one goes up, the other generally goes down.

Hyperparathyroidism: Causes and Types

Hyperparathyroidism occurs when one or more glands secrete excessive PTH, leading to hypercalcemia. It is categorized into three main types:

1. Primary Hyperparathyroidism: Caused by a benign adenoma, hyperplasia, or rarely carcinoma of the parathyroid glands. PTH and calcium levels are both elevated.
2. Secondary Hyperparathyroidism: A compensatory response to chronic hypocalcemia, most commonly seen in chronic kidney disease where the kidneys fail to activate vitamin D or excrete phosphate.
3. Tertiary Hyperparathyroidism: Occurs when hyperplasia of the glands becomes autonomous and continues to secrete high PTH despite the correction of chronic kidney disease, often requiring surgical removal.

Hypoparathyroidism: Causes and Types

Hypoparathyroidism is a rare condition characterized by insufficient PTH production, leading to hypocalcemia and hyperphosphatemia. The vast majority of cases are iatrogenic, resulting from the inadvertent removal of or damage to the parathyroid glands during thyroidectomy, parathyroidectomy, or radical neck dissection. Idiopathic hypoparathyroidism can also occur due to autoimmune destruction or genetic syndromes like DiGeorge syndrome.

Clinical Manifestations of Parathyroid Imbalances

Clinical signs depend heavily on whether the patient has too much or too little calcium.

• Hypercalcemia (Hyperparathyroidism): Often summarized as 'stones, bones, groans, and psychiatric moans.' Symptoms include kidney stones, bone pain, abdominal cramps, constipation, nausea, fatigue, and depression.
• Hypocalcemia (Hypoparathyroidism): Causes neuromuscular irritability. Nurses check for Trousseau's sign (carpal spasm after inflating a blood pressure cuff) and Chvostek's sign (facial twitching when tapping the facial nerve). Severe cases present with tetany, laryngeal stridor, and seizures.

Diagnostic Evaluation and Laboratory Findings

Diagnosing parathyroid disorders requires a combination of blood tests, imaging, and functional assessment. Serum intact PTH levels are measured alongside total and ionized calcium, serum phosphate, and alkaline phosphatase. Imaging studies such as sestamibi scans, neck ultrasounds, and CT scans help localize abnormal glands or adenomas before surgical exploration.

Medical and Pharmacological Management

Medical management varies drastically depending on the underlying hormonal imbalance.

• Hyperparathyroidism: Mild asymptomatic cases are monitored with hydration and weight-bearing exercise. Medications include calcimimetics (such as cinacalcet) to trick the calcium sensing receptors, bisphosphonates to protect bones, and loop diuretics to promote calcium excretion.
• Hypoparathyroidism: Managed with oral calcium supplements and active vitamin D metabolites like calcitriol to enhance intestinal absorption. Thiazide diuretics may be used if hypercalciuria develops.

Surgical Intervention: Parathyroidectomy

Surgical removal of abnormal parathyroid tissue is the definitive cure for primary hyperparathyroidism. Surgeons may perform a minimally invasive radioguided parathyroidectomy if a single adenoma is localized, or a bilateral neck exploration if multiple glands are enlarged. Intraoperative PTH monitoring is frequently used; because PTH has a very short half-life of about 3 to 5 minutes, a sudden drop in levels after gland removal confirms surgical success.

Nursing Care Plan and Patient Education

Postoperative nursing care focuses on monitoring airway patency, managing pain, and watching for sudden electrolyte shifts. Because of the close anatomical proximity of the parathyroid glands to the recurrent laryngeal nerves and the thyroid, nurses must assess the patient's voice quality for hoarseness and keep emergency tracheostomy equipment nearby. Nurses should also watch closely for signs of hypocalcemic tetany following parathyroidectomy, ensuring intravenous calcium gluconate is readily available at the bedside.