الفهرس 
Anatomy and embryology of Parathyroid GlandsOnly 14 pages are availabe for public view
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Abstract
Hyperparathyroidism is a serious metabolic disorder, The incidence of hyperparathyroidism is about one in 20.000 people. The incidence of hyperparathyroidism has increased substantially, largely as a result of routine blood calcium measurement. Primary hyperparathyroidism is usually a disease of adults, most cases occur in the fifties or later in life, it is more common in women than in men, and most prevalent in postmenopausal women. Of all patients with PHPT, approximately 87% have a single adenoma while only 9% have four-gland hyperplasia, 3% have double adenomas, and 1% have parathyroid carcinoma , Although most patients with Primary Hyperparathyroidism have sporadic disease, some Patients have primary hyperpara-thyoidism associated with familial endocrinopathies, including multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2 (MEN 2), familial hyperparathyroidism without other endo-crinepathies and neonatal hyperparathyroidism.
The most common presentation of PHPT is the detection of unsuspected asymptomatic hypercalcemia by routine biochemical screening diagnosis of hyperparathyroidism is based upon 2 laboratory tests alone: serum calcium, and serum parathyroid hormone.
Most authors favor the measurement of ionized calcium, which is directly affected by parathyroid hormone. Ultrasonography and Technetium99m-sesta-mibi are standard modalities for imaging parathyroid lesions. A bilateral neck exploration, unilateral neck exploration or minimally invasive radio-guided parat-hyroiddectomy may be pursued conditional based on the results from these localization scans. Other pre-operative localization studies include CT scan, MRI, Technetium 99m-Tetrofosmin scanning, Thalium-Technetium subtraction scintigraphy, Positron Emission Tomography (PET) scanning, with invasive modalities like fine needle aspiration and selective angiography with venous sampling. In addition to being a valuable adjunct to confirm the completeness of parathyroid resection, the rapid PTH assay has been shown to be a useful adjunct, unilateral exploration. Some authors have used intra-operative PTH to help localize the disease in cases where a sestamibi scan has failed to identify the pathology. other intra-operative investigations include U/S, gamma probe nuclear imaging, methyline blue, and frozen section. Surgical management of primary hyperparathyroidism is a very effective method. The target is to cure primary hyperparathyroidism and to reach normal calcium levels. This results in an improvement of health condition and resolution or at least moderation of symptoms.
Complications are infrequent and mortality is very low. Surgical management is definite, safe and effective. Operative management should also be considered for all other asymptomatic patients with suitable risk and a reasonable life expectancy. While bilateral neck exploration has been the mainstay of therapy, recent advances in technology have revolutionized the field making a focused approach to parathyroidectomy a reality. The development of accurate pre-operative localization, effective unilateral, endoscopic, radio-guided and video-assisted techniques, and rapid intra-operative parathyroid hormone (PTH) testing have made it possible to cure patients with the least amount of surgical dissection possible Parathyroid exploration could be carried out under local anaesthesia, especially for patients at high risk of general anaesthesia, with reasonable results. For patients not fit for surgery, ethanol, angiographic and U/S guided laser ablation can be used.
While earlier detection has made the classic symptoms of nephrolithiasis and severe bone disease less frequent than before, there is evidence that many patients present with fatigue, irritability, and other non specific symptoms, parathyroidectomy has been shown to cause significant improvement in these symptoms Furthermore, parathyroidectomy reduces the incidence of recurrent nephrolithiasis by 90% increases bone mineral density, improves left ventricular hypertrophy tightens blood glucose control, and enhances quality life and self-rated health.
Secondary Hyperparathyroidism
This disorder occurs most often in individuals with end-stage renal failure but may also occur in other conditions resulting in hypocalcemia such as vitamin D deficiency, idiopathic hypercalciuria, hypermagnesemia, and long-term lithium therapy. Indications for surgery include situations where the product of serum calcium and phosphate is >70, renal osteodystrophy with bone pain, severe pruritus, ectopic soft tissue calcifications and tumoral calcinosis, serum calcium >11mg/dL with markedly elevated PTH, and calciphylaxis. These patients should undergo dialysis the day prior to surgery to correct electrolyte (specifically potassium) abnor-malities.
Patients with this disorder require bilateral exploration and either subtotal parathyroidectomy, leaving a 50-60mg histologically confirmed well-vascularized remnant of hyperplastic parathyroid distant from the recurrent laryngeal nerve; or total parathyroidectomy with autotransplantation of a similar amount of tissue. The former is usually preferred, as not all autografts function. Upper thymectomy is usually performed in these patients, since up to 15% of patients will have a fifth hyperplastic gland.
Tertiary Hyperparathyroidism is a sequel to long-standing secondary hyperparathyroidism. Tertiary disease is characterized by the development of autonomous hypersecretion of PTH causing hypercalcemia. The etiology is unknown. A change in the set point of the calcium sensing mechanism to hypercalcemia levels appears to exist. Tertiary hyperparathyroidism is observed most commonly in patients with chronic secondary hyperparathyroidism and often after renal transplantation. The hypertrophied parathyroid glands fast return to normal and continue to oversecrete PTH, despite serum calcium levels that are within the reference range or even elevated.
In these cases, the hypertrophied glands become autonomic and cause hypercalcemia, even after withdrawal of calcium and calcitriol therapy. This type of tertiary is particularly dangerous because the phosphate level often is elevated. If the calcium times phosphate product is high, diffuse calcinosis may occur. Clinical presentation of tertiary hyperpara-thyroidism includes persistent hyperparathyroidism after transplantation or new hypercalcemia in the setting of chronic secondary hyperparathyroidism, Total parathyroidectomy with autotransplantation or subtotal parathyroidectomy is indicated.