Primary hyperparathyroidism refers to excessive secretion of parathyroid hormone (PTH) by the parathyroid glands, leading to disturbances in calcium, phosphate, and bone metabolism. This condition is commonly abbreviated as "primary hyperparathyroidism" and is a surgically curable disease more frequently observed in Western countries such as those in Europe and North America.
Pathology
Primary hyperparathyroidism includes parathyroid adenoma, hyperplasia, and carcinoma. Parathyroid adenoma is the most prevalent, accounting for approximately 85% of all cases of primary hyperparathyroidism, and is often solitary. Parathyroid hyperplasia comprises around 12% of cases, with all four glands potentially affected. Parathyroid carcinoma is rare, accounting for only 1% to 2% of cases.
Clinical Manifestations
The condition comprises two categories: asymptomatic and symptomatic types. Asymptomatic patients often exhibit no obvious symptoms or only nonspecific manifestations such as osteoporosis. These cases are typically diagnosed during routine health screenings due to elevated serum calcium levels. Symptomatic primary hyperparathyroidism remains more prevalent, although the proportion of asymptomatic patients is steadily increasing.
Symptomatic cases present as one of three subtypes:
- Type I: This is the most common, primarily characterized by bony disease and often referred to as the "bone type." Patients may report bone pain and are prone to fractures. Subperiosteal bone resorption, a distinctive feature of the disease, is most frequently observed on the radial side of the middle finger or the lateral one-third of the clavicle.
- Type II: This subtype manifests predominantly as kidney stones and is referred to as the "renal type." Approximately 3% of patients with urinary tract stones are found to have parathyroid adenomas. Severe cases may lead to renal failure.
- Type III: This category displays features of both bone and renal types, presenting with skeletal changes alongside urinary tract stones.
Other possible symptoms include peptic ulcers, neuropsychiatric symptoms, weakness, and joint pain.
Diagnosis
The diagnosis is primarily based on clinical features, supplemented by laboratory and localization studies.
Laboratory Tests
Serum Calcium Measurement
Elevated serum calcium levels serve as a key indicator for diagnosing hyperparathyroidism. The majority of patients exhibit serum calcium values exceeding the normal range, which typically falls between 2.25 and 2.58 mmol/L.
PTH Measurement
Elevated PTH levels provide the most reliable and direct evidence for diagnosing primary hyperparathyroidism, with values often reaching several times the normal range.
Serum Phosphorus Measurement
Some patients present with hypophosphatemia, although it has less diagnostic value compared to serum calcium.
Localization Studies
Ultrasound Examination
This method is commonly used to locate abnormal parathyroid glands, although it may be less effective for ectopic glands.
Radionuclide Imaging
The use of 99mTc-MIBI (technetium-99m methoxyisobutylisonitrile) is widely employed and shows satisfactory results, with a localization accuracy exceeding 90%. It is particularly useful for identifying ectopic parathyroid glands.
Enhanced Neck CT
This imaging modality visualizes the anatomical relationship between the affected parathyroid glands and surrounding tissues. It provides precise preoperative localization and offers high sensitivity in detecting ectopic parathyroid glands.
Treatment
Surgical intervention serves as the primary treatment, and the approach may involve either open surgery or minimally invasive laparoscopic techniques. Intraoperative frozen section examination and the confirmation of reduced calcium and PTH levels following lesion removal can assist in establishing a definitive diagnosis.
Parathyroid Adenoma
The primary treatment involves resection of the adenoma, which yields good outcomes in early-stage cases. In patients with a long disease course and renal impairment, adenoma removal can halt the continued damage to renal function caused by hyperparathyroidism. However, for cases with severe pre-existing renal damage, the therapeutic effect is suboptimal.
Parathyroid Hyperplasia
Two surgical approaches are available: one involves subtotal parathyroidectomy, wherein 3 1/2 glands are resected, leaving 1/2 gland intact. The other approach entails removing all four parathyroid glands, followed by autotransplantation of parathyroid tissue. Additionally, a portion of the tissue may be cryopreserved for potential future use if necessary.
Parathyroid Carcinoma
The recommended surgical procedure involves en bloc resection of the parathyroid tumor along with the ipsilateral thyroid lobe and isthmus, as well as dissection of lymph nodes in the ipsilateral central neck compartment. If the tumor invades the surrounding soft tissues, extensive resection of the affected tissues is required.
Surgical Complications and Postoperative Management
Complications are rare. In exceptional cases, pancreatitis may develop postoperatively, although the underlying cause remains unclear. Extensive exploration or careless operative maneuvers may result in damage to the recurrent laryngeal nerve.
Serum calcium levels typically decline significantly within 24–48 hours after surgery. Patients may report numbness in the face, perioral area, or extremities, and severe cases may experience tetany. These symptoms generally resolve within 3–4 days postoperatively. For patients with severe and prolonged hypocalcemia, oral calcium supplements and vitamin D may be added to treatment regimens.
Postoperative declines in serum calcium levels often suggest successful surgical removal of the pathological glands.