Enlarged parathyroid gland

A 28-year-old female with a history of hypertension and chronic kidney disease. The patient started with bone pain and proximal muscle weakness, with an overall unremarkable physical exam. Laboratory testing found hypercalcemia (15 mg/dl) and PTH level elevated at 1400 pg/mL.

Pathology: Parathyroid, excision: the parotid gland weighs 6.9 grams.

Early and delayed 99mTc-MIBI single photon emission computed tomography/computed tomography (SPECT/CT) was performed. The CT scan revealed the presence of a space-occupying lesion in the parathyroid parenchyma, while the SPECT scan displayed abnormal accumulation of 99mTc-MIBI relative to the neck muscles and blood vessels.

Thyroid ultrasound was conducted and showed four oval, well-defined, hypoechogenic, and homogeneous lesions posterior to the right and left lobes of the thyroid gland. The maximum longitudinal diameter of the largest was 21.5 mm. An increased flow signal was demonstrated with a vascular pedicle and a vascular arch localized at the periphery of the gland.

Contrast-enhanced ultrasound was performed and demonstrated intranodular and pedicle hyperenhancement compared with sounded tissues (white arrows) in the early phase and wash out in the late phase.

The nodule underwent fine-needle aspiration and cytology. The cytology samples with hematoxylin and eosin staining revealed monolayer cells with regular nuclei and oxyphilic cytoplasm.

The patient underwent a total thyroidectomy and showed parathyroid tissue with a smooth surface, light brown colour, solid appearance, and a soft consistency, with areas of haemorrhage alternating with white areas. A low-power microscopic view revealed a solid and cribriform tissue made up of monotonous-looking cells with eosinophilic cytoplasm, round nuclei, and homogeneous and fine chromatin. A high-power microscopic view showed chief cell proliferation involving all 4 glands in relation to parathyroid hyperplasia.

Parathyroid hormone is crucial for maintaining optimal calcium homeostasis. Hence, the term secondary hyperparathyroidism is frequently applied to characterize a compensatory phenomenon whose purpose is diminished bioavailability of calcium and/or vitamin D and induces parathyroid hyperplasia [1].

The most prevalent cause of parathyroid hyperplasia is chronic kidney disease. Renal function impairment involves downregulation of parathyroid vitamin D and calcium-sensing receptors, producing a decline in mineral metabolism and leading to hyperphosphatemia, hypocalcemia, and vitamin D insufficiency [2].

The typical clinical manifestation is bone fractures, and it is a deleterious condition because their occurrence is related to an increased risk of death [3].

The diagnosis of hyperparathyroidism relies on the detection of increased levels of PTH. The diagnostic difference between primary and secondary hyperparathyroidism is primarily based on the presence of high or low blood calcium levels, respectively [4].

Ultrasonography is the most used imaging modality due to its availability, affordability, and simple manipulation, and has a sensitivity of 75.65%, but the accuracy depends on the examiner's experience [5]. The hyperplastic parathyroid are visible as oval, symmetrical, hypoechogenic nodule in the posterior border of thyroid gland. The maximum longitudinal diameter and volume of the largest parathyroids were observed to be connected to the severity of secondary hyperparathyroidism. A Doppler examination may be able to detect the parathyroid vascular pedicle and a vascular arch localized at the periphery of the gland [6].

Contrast-enhanced ultrasound considerably enhances spatial resolution, properly evaluates the blood supply of a lesion, separates the lesion from surrounding tissues, and offers an index to judge the perfusion of nodules compared with adjacent tissue. The parathyroid gland demonstrates quick hyper-and iso-enhancement, simplifying identification and minimizing intraoperative risk [7].

Parathyroid Scintigraphy is a functional study focused on the capture of a radiotracer by the hyperfunctional parathyroids. Two distinct scintigraphy methods are recognized. The single tracer technique is based on scanning the cervical area in two stages, in an early phase at 10–30 minutes and a late phase at 90–180 minutes. The double tracer and subtraction technique uses two tracers, 99mTc-sestamibi and a thyroid tissue-specific tracer (Technetium-99m-pertechnet or 123 I). The acquisition of the images for each radiotracer is undertaken, and then the subtraction is computerized; "the image" of the thyroid gland is attenuated, thereby highlighting just the capture in the parathyroid glands [8].

In patients with CKD requiring PTH-lowering medication, the first line of treatment is medication. Parathyroidectomy (PTx) is considered in individuals with hyperparathyroidism unresponsive to conservative medicinal treatment. The use of PTx in patients with CKD is related with improvements in biochemical indicators of mineral and bone metabolism, cardiovascular health, and mortality [9].

Numerous investigations have determined the necessary intravenous or oral calcium supplementation following parathyroidectomy. Although the objectives of maintaining normokalaemia or rectifying hypocalcemia were not explicitly stated, factors such as elevated preoperative parathyroid hormone and alkaline phosphatase levels, as well as decreased serum calcium levels, were identified as significant predictors of increased calcium requirements [10].

Take Home Message / Teaching Points

• SHP is one of the most prevalent complications in people with chronic renal failure.
• The diagnosis of hyperparathyroidism relies on the detection of elevated levels of PTH. The diagnostic distinction between primary and secondary hyperparathyroidism is essentially dependent on the presence of high or low blood calcium levels, respectively.
• The first-line studies are the ultrasonography of the cervical area and parathyroid scintigraphy, which should be done in all patients.
• Contrast-enhanced ultrasound (CEUS) greatly boosts spatial resolution, appropriately analyses the blood supply of a lesion, differentiates the lesion from surrounding tissues, and gives an index to estimate the perfusion of nodules compared with neighbouring tissue.
• The number of accessible medications for the treatment of SHP has constantly expanded in the previous decade. Furthermore, a steady percentage of SHP still advances toward the uncontrolled form of SHP, which typically requires a surgical approach.

Written informed patient consent for publication has been obtained.