Hyperparathyroidism in Otolaryngology and Facial Plastic Surgery Workup

Updated: Nov 16, 2015
  • Author: James LaBagnara, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Laboratory Studies

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  • Diagnosis is made based on hypercalcemia and elevated parathyroid hormone (PTH) levels. Other abnormal laboratory findings may include elevated BUN and creatinine levels, hyperchloremic acidosis, reduced serum bicarbonate levels due to renal bicarbonate casting, hypophosphatemia, elevated alkaline phosphatase levels and hypercalciuria.

  • Other causes of hypercalcemia (eg, paraneoplastic syndromes, malignancies, Paget disease, drug-induced causes, dietary causes) are not associated with PTH level elevation. However, occasionally, primary hyperparathyroidism and malignancy-related hypercalcemia may coexist.

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Imaging Studies

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  • The importance of preoperative localization studies can substantially reduce operative time, cost, and patient morbidity. This is important in the era of managed care and operating room cost containment. Without preoperative localization, a parathyroid adenoma is successfully identified and removed in more than 95% of patients, although this may require exploration of all 4 glands.

  • Accurate localization can limit exploration to the identified side, allowing rapid removal of the adenoma. If a second adenoma is present, both adenomas are frequently identified with preoperative ultrasonography and sestamibi scan, even if the lesion is in an ectopic location. Localization may not reduce the need for a later reexploration for a mediastinal adenoma. A list of noninvasive imaging modalities and their usefulness and ease of performance appears below, in order of increasing cost, as follows:

    • High-resolution ultrasonography: In the hands of an experienced ultrasonographer, this method is the most economic and may provide maximum information. It shows enlarged parathyroid glands and their relationship to relevant neck anatomy, thyroid nodules, and lymph nodes. High-resolution ultrasonography can reveal multiple adenomas, hyperplasia of all 4 glands, and glands in ectopic cervical locations such as within the carotid sheath or thyroid. However, high-resolution ultrasonography can not identify mediastinal adenomas.

    • Technetium-99m labeled sestamibi scan

      • This nuclear material has a specific affinity for abnormal parathyroid tissue. Although uptake also occurs in thyroid tissue, technetium-99m rapidly diminishes in the thyroid but is retained in the parathyroid mitochondria.

      • Sestamibi scan is useful in identifying single and multiple parathyroid adenomas and hyperplasia. Sestamibi also can reveal ectopic glands.

      • Although sestamibi is most often used preoperatively, it can also be used intraoperatively. Intrathoracic adenomas can also be identified despite the overlying sternum. A sestamibi scan that fails to reveal an adenoma in a patient with hypercalcemia and elevated PTH levels may suggest diffuse hyperplasia of all 4 glands or the presence of an adenoma that has a cell population that consists mainly of chief cells.

      • Although sestamibi is very sensitive with single adenomas, it fails to reveal 17% of second adenomas and 55% of hyperplastic glands. The outcome of the sestamibi scan is most influenced by the size of the adenoma; scans of lesions less than 2 cm in size are often difficult to interpret. Since sestamibi is concentrated in mitochondria, the sensitivity of sestamibi has histopathologic considerations that vary by the predominant cell type within the adenoma.

      • Adenomas that are rich in Oxyphil cells have a higher mitochondrial content, greater metabolic activity, and increased radiotracer uptake. Adenomas that are predominantly chief cells have minimal mitochondrial content and minimal radiotracer uptake.

    • CT scan: CT scanning provides excellent spatial resolution and greater detail than the images obtained in a single plane. CT scans can be reconstructed for additional views. The location of an enlarged gland can be precisely defined in relation to adjacent anatomy. CT scan is helpful in locating mediastinal adenomas as well.

    • MRI: MRI provides excellent contrast resolution; images can be formatted in multiple planes (ie, axial, coronal, sagittal). Increased vascularity of the adenomas is ideal for identification with this modality. MRI may be useful in locating mediastinal adenomas.

  • Combination of ultrasonography and sestamibi scan provides maximum information and is cost effective.

  • CT scan or MRI for mediastinum adenomas may be required when an adenoma is suspected in the thorax.

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Histologic Findings

In primary hyperparathyroidism, the adenomas represent true neoplasms. Diffuse hyperplasia occurs in the absence of an adenoma. Hyperplasia of all 4 glands is often dramatic in renal (secondary) hyperparathyroidism with significantly increased gland volumes and weights.

Frozen section differentiation of an adenoma from hyperplasia is difficult for the pathologist. In the operating room, the surgeon primarily wishes to know that the specimen contains parathyroid tissue. An adenoma can be identified on permanent section if the surrounding halo or rim of fat is visible along with certain cellular characteristics. An experienced surgeon can usually identify an adenoma in situ based on its size and color as compared with a normal parathyroid gland, lymph node, or globule of fat.

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