Primary hyperparathyroidism is caused by overactive parathyroid glands, leading to elevated calcium levels in the blood. The standard preoperative imaging includes both a radiation-based imaging modality and conventional ultrasound. However, ultrasound alone is a faster, safer, and more patient-friendly alternative. This study evaluates an upfront ultrasound approach, where patients undergo ultrasound first, and only those with certain findings proceed directly to surgery without additional imaging. Patients with uncertain findings proceed to additional imaging. The study is designed as a prospective cohort with a non-inferiority analysis, aiming to confirm whether upfront ultrasound can achieve an acceptable diagnostic sensitivity. If successful, this approach could reduce patient burden, minimize radiation exposure, and optimize healthcare resources

This study evaluates the implementation of a stepwise approach using upfront ultrasound for localizing pathological parathyroid glands in patients with primary hyperparathyroidism (PHPT).

PHPT is caused by overactive parathyroid glands, leading to excessive amounts of calcium in the blood, which can result in complications such as kidney stones, osteoporosis, cardiovascular disease, and neurological symptoms. The standard preoperative imaging process currently includes both nuclear medicine scans and ultrasound. However, nuclear imaging is time-consuming, exposes patients to radiation, and may not always provide definitive results.

The proposed approach prioritizes ultrasound as the initial localization tool, with additional imaging reserved for cases where ultrasound findings are inconclusive. This method has the potential to reduce unnecessary hospital visits, minimize radiation exposure, and streamline the diagnostic process. The study aims to ensure that this approach maintains high sensitivity for the localization of pathological parathyroid glands, with a target sensitivity of at least 89.5% for correctly identifying diseased parathyroid glands.

Designed as a prospective cohort study, the project will assess patients using ultrasound first, assigning confidence scores (0-3) to determine whether further imaging is necessary. A confidence-score of 3 indicates a high diagnostic confidence. To gain a score of 3, the potential parathyroid adenoma must meet all predefined criteria, i.e. hypoechogenicity, well-defined margins, location at the anatomically expected position, a polar feeding vessel, and a vascular arc. A diagnostic-score of 2 reflects moderate suspicion, where one or two of these key features are missing. A diagnostic-score of 1 suggests low suspicion, typically characterized by a poorly defined structure with no vascular features. Finally, a diagnostic-score of 0 means that no potential adenoma was detected.

Postoperative findings will confirm the accuracy of the preoperative imaging with the histopathological result of the surgically removed specimen(s) combined with biochemical cure at 6 months as the reference standard.

The study aims to benefit both patients and society as it intends to decrease patient exposure to radiation, reduce costs, and reduce the time patients have to take off from work for the purpose of preoperative imaging. One less hospital visit will also reduce the pollution caused by an extra day of transportation to and from the hospital.

Inclusion Criteria:

• Patients 18 years and older with primary hyperparathyroidism referred to the Department of ORL, Head and Neck Surgery at Odense University Hospital for parathyroidectomy.

Exclusion Criteria:

• Other causes of hypercalcemia
• Persistent or recurrent hyperparathyroidism.
• Previous surgery to the thyroid or the parathyroid glands.
• Inability to read/speak Danish

Patients 18 years and older with primary hyperparathyroidism referred to the Department of ORL, Head and Neck Surgery at Odense University Hospital for parathyroidectomy.