Introduction

Primary hyperparathyroidism (PHPT) is due to an increased secretion of parathyroid hormone (PTH). It is the most common cause of hypercalcemia, above all, during postmenopause. It was described for the first time back in 1930¹.

Both its rate and prevalence have increased over the past decades thanks to the greater detection of mild hypercalcemia with the use of more biochemical tests with serum calcium that has increased the number of diagnoses of asymptomatic cases of PHPT. Its significance lies in its progression: up to a fourth of all patients ends up developing symptoms within the next 5 years^1,2.

A total of 80% of all PHPTs are benign parathyroid adenomas, 15% to 20% are parathyroid hyperplasias, and less than 1% parathyroid carcinomas¹.

Ectopic parathyroid glands (EPG), described in up to 16% of the cases, are due to the anomalous migration of these during development. They can be found in tissues that share their embryologic origin³. Imaging modalities are important for the diagnosis, location, and surgical planning of this entity. Parathyroidectomy (PT) is the ultimate treatment here^3,4.

This is the case report of a female patient with PHPT due to ectopic parathyroid adenoma.

Clinical signs

This is the case of a 39-year-old woman with multiple episodes of urinary tract infections, renal colics, and nephrolithiasis. She presents with weakness, chronic fatigue, and hypercalcemia (10.9 mg/dL). PTH is analyzed and since elevated levels are found (138.3 pg/mL) PHPT is finally diagnosed.

Management of the patient included a computed tomography scan (see Figure 1) and a gammagraphy with Tc99-sestamibi (Figure 2) that revealed the presence of ectopic parathyroid adenoma of superior mediastinum location. Transverse cervicotomy access was used and medium sternotomy with pneumatic saw was performed under balanced general anesthesia. The radio-and-gamma probe guided minimally invasive parathyroidectomy performed revealed the presence of parathyroid adenoma at mediastinum level (Figure 3) that was resected uneventfully (Figure 4). No events were reported during the postoperative period resulting in lower levels of calcium and PTH.

Figure 1.  Computed tomography scan. Panel A: Sagittal view showing ectopic parathyroid adenoma 2 cm away from the sternal notch. Panel B: Axial view showing an oval-shaped nodular image with demarcated borders. 

Figure 2.  Images acquired through parathyroid gammagraphy with 99mTc-Sestamib showing the ectopic parathyroid adenoma at the superior mediastinum central region. 

Figure 3.  Transoperative image of ectopic parathyroid adenoma at superior mediastinal level. 

Figure 4.  Resection of ectopic parathyroid adenoma measuring 2 cm x 1.6 cm x 0.8 cm and weighting 1.7 g.  

Discussion

PHPT is more common in women on a 4:1 ratio compared to men. The highest incidence rate has been reported within the first few years after menopause, which is consistent with estrogen loss. Up to 20% of the patients have a past medical history of renal colics¹. Our case is consistent with the cases reported in the medical literature available today.

There are 3 different presentations of PHPT: symptomatic or classic (elevated calcium and PTH levels), asymptomatic or normohormonal (elevated calcium and normal PTH levels) and normocalcemic (normal calcium and elevated PTH levels). The latter can be a precursor of traditional PHPT^{(1, 2)}. Our patient had classic signs.

The risk factors reported are low calcium intake, low physical activity, large abdominal circumference, obesity, hypertension, neck radiation or nuclear exposure and prolonged lithium therapy¹.

Up to 16% of the patients show EPG. Three different studies concluded that the most common regions are the thymus, the retro/paraesophageal space, and thyroid, which represent 56% to 89% combined. Between 6% and 26% have been described in the mediastinum^5,6.

Signs and symptoms are due to hypercalcemia, among them, fatigue, weakness, polyuria, polydipsia, constipation, anorexia, vomiting, dehydration, arrhythmias, anxiety, altered mental state, and mood swings. Our patient also complained of fatigue, and chronic weakness¹. Frailty-induced fractures, skeletal deformities, and bone pain are also possible. Also, presentation through hypercalciuria, nephrolithiasis, nephrocalcinosis, and reduced renal function¹, as it happened in our case and its presentation of classical phenotype.

Diagnosis is achieved after detecting elevated hypercalcemia. Also, elevated PTH levels with ≥ 20 pg/mL in the context of hypercalcemia is consistent with the diagnosis^1,7.

Preoperative imaging modalities facilitate surgery by accurately finding the adenoma like ultrasound, gammagraphy with 99m-tecnecium-sestamibi, computed tomography scan, magnetic resonance imaging, and PET⁸. Gammagraphy has higher sensitivity (89%) and ultrasound has less sensitivity (59% to 76%) although the latter is more widely available. Gammagraphy is considered the gold standard^3,8.

Surgery is clearly indicated in patients with symptoms due to hypercalcemia or target organ failure (frailty-induced fractures or colics)^1,7. Definitive treatment of choice is parathyroidectomy⁸. Cervical approach is often enough. However, 2% of the cases of mediastinal location require transsternal or transthoracic approach³.

The rates of healing for an experienced surgeon exceed 95% with a very low rate of complications (< 1% to 3 %) like hemorrhages, hypocalcemia, and recurring laryngeal never injuries^1,2. Once parathyroidectomy has been performed, biochemical markers often go back to normal, and bone density goes up, thus reducing the risk of fracture and nephrolithiasis⁸.