Primary parathyroid hyperplasia

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For patient information, click Insert page name here Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Synonyms and keywords: Hyperplasia of the parathyroid gland

Overview

Parathyroid hyperplasia is the diffuse enlargement of the parathyroid glands and is a cause of primary hyperparathyroidism. Parathyroid hyperplasia may be classified into 2 subtypes: primary parathyroid hyperplasia and secondary parathyroid hyperplasia.

Classification

• Primary parathyroid hyperplasia
• Secondary parathyroid hyperplasia

Pathophysiology

• Parathyroid hyperplasia is the diffuse enlargement of the parathyroid glands and is a cause of primary hyperparathyroidism
• In ~50% of cases there is asymmetric enlargement of the parathyroid glands.

Associated Conditions

• Multiple endocrine neoplasia I (MEN I)
• Multiple endocrine neoplasia II A (MEN IIA)
• Isolated familial hyperparathyroidism

Gross Pathology

• Classically all parathyroid glands are involved; however, some may be spared making it difficult to differentiate this from parathyroid adenoma.

Microscopic Pathology

• Classically have abundant adipose tissue
• +/-Water-clear cells ("water-clear cell hyperplasia").

Hyperplasia of parathyroid gland HE-staining, 20× magnification.

Causes

• Primary parathyroid hyperplasia

• Sporadic (80%): associated with exposure to radiation and lithium
• Familial (20%): associated with MEN 1 and MEN 2a

• Secondary parathyroid hyperplasia

• Renal failure

Differentiating type page name here from other Diseases

• Parathyroid adenoma
• Parathyroid carcinoma

Epidemiology and Demographics

Age

Females are more commonly affected with parathyroid hyperplasia than males. The females to male ratio is approximately 3:1.

Risk Factors

• Multiple endocrine neoplasia I
• Multiple endocrine neoplasia II A
• Isolated familial hyperparathyroidism

Natural History, Complications and Prognosis

• Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as excellent.

Complications

• Kidney stones
• Osteitis fibrosa cystica

Diagnosis

Symptoms

• Constipation
• Bone fractures or bone pain
• Nausea
• Lethargy
• Muscle pain

Alcohol

The frequency and amount of alcohol consumption should be characterized.

Laboratory Findings

• Calcium
• Phosphorus
• Magnesium
• PTH
• Vitamin D levels
• A 24-hour urine test

Chest X Ray

• Bone x-rays

Other Imaging Findings

• Bone density test (DXA)
• Nuclear medicine (Tc-99m MIBI) is the current modality of choice.

Treatment

Surgery

• Surgery is the mainstay of treatment for parathyroid hyperplasia. Three and a half part of the glands are removed during surgery.

Parathyroidectomy

• Patients with primary hyperparathyroidism and concordant localisation to a single site can undergo minimally invasive parathyroidectomy. Patients with primary hyperparathyroidism where localisation has not been successful are more likely to have multiple gland disease and should undergo open parathyroidectomy and four-gland exploration. Patients with secondary and tertiary hyperparathyroidism require either subtotal parathyroidectomy or total parathyroidectomy with or without forearm autotransplantation. Successful detection and removal of the involved parathyroid tissue will occur in 98% of patients. In the small percentage of patients in whom the gland is not detected at the time of primary surgery, it is likely to lie in an ectopic position, e.g. pericardium or middle mediastinum and additional, localisation studies such as CT scanning and selective venous sampling will be required prior to a second operation.

Complications of parathyroidectomy

• The complications of parathyroidectomy include all the general complications of any operation, such as bleeding, wound infection, and reaction to the anaesthetic agent. In addition, there are specific complications, including: damage to the recurrent laryngeal nerves and to the external branch of the superior laryngeal nerves failure to locate abnormal parathyroid tissue hypoparathyroidism
• Recurrent nerve palsy leads to a hoarse voice that usually recovers but may require procedures such as vocal cord medialisation. If the external branch of the superior laryngeal nerve is damaged, the patient may lose the ability to sing, shout or project their voice. Failure to locate abnormal parathyroid tissue may be due to the adenoma being in an ectopic site such as the mediastinum. Further localisation studies and surgery will be required. If more than one parathyroid gland is involved, subtotal parathyroidectomy may lead to hypoparathyroidism, which may require short-term administration of oral calcium and 1,25-dihydroxyvitamin D for several weeks.

Secondary Prevention

• Genetic screening for patients with family history of MEN syndrome.