Hyperparathyroidism

Generality

Hyperparathyroidism is a clinical condition related to excessive parathyroid hormone synthesis and secretion.

It therefore involves the parathyroids, four small glands located two by two on the dorsal aspect of the thyroid, similar to lentils and deputed to the synthesis of parathormone (PTH) and to its release in the blood; in turn, this protein hormone has a hypercalcemizing effect, increasing the mobilization of calcium from the bones, stimulating intestinal absorption (mediated by vitamin D) and decreasing urinary excretion.

For this reason most forms of hyperparathyroidism are accompanied by an increased concentration of calcium in the blood, a condition known as hypercalcemia .

The biological role of paratharmony is counteracted by calcitonin, which after being synthesized and secreted by the thyroid promotes the deposition of calcium in the bones.

Insights

Causes of hyperparathyroidism Risk factors Hyperparathyroidism symptoms Diagnosis Treatment

Causes

Hyperparathyroidism may be consequent to:

autonomous and exaggerated parathyroid secretion by one or more parathyroids (primary hyperparathyroidism);
excessive parathormone secretion - in the absence of an intrinsic parathyroid disease - caused by the response to hypocalcemia (secondary hyperparathyroidism).

Primary hyperparathyroidism

In 85% of cases the origin of primary hyperparathyroidism is linked to a benign tumor (adenoma) of the parathyroid glands. At other times (14% of cases) the condition is related to the increase in volume of one or more glands; in these circumstances we speak of parathyroid hyperplasia. Very rarely (1% of cases), at the origin of the problem there is instead a malignant tumor, called parathyroid carcinoma. Whatever its origin, the excessive secretion of parathormone causes a rise in calcium in the blood; in the long run the bones tend to demineralize and fracture easily, while the amount of alimentary calcium absorbed at an enteric level tends to increase. Consequently, the urinary excretion of calcium also rises (despite the physiological effect of the parathormone having the opposite effect) and of phosphorus, exposing the subject to a greater risk of kidney stones.

Secondary hyperparathyroidism

Secondary hyperparathyroidism reflects parathyroid hormone hypersecretion in response to reduced body calcium levels; this compensatory parathyroid hyperactivity - which results in hyperlplasia of the same glands with hypersecretion of parathormone - can therefore be due to a lack of calcium and / or vitamin D, as well as an important defect in intestinal mineral absorption (syndrome of malabsorption, as occurs in celiacs or in individuals suffering from chronic intestinal inflammatory diseases). The most frequent cause of secondary hyperparathyroidism, at least in industrialized countries, is however represented by chronic renal failure; we recall in fact that the kidney has a fundamental role in the activation of vitamin D. Moreover, in chronic renal failure the increase in phosphatemia favors a further and progressive reduction of calcemia.

Risk factors

The risk of hyperparathyroidism is slightly greater for women than for men (3: 2), especially in the first years after menopause. As mentioned, even those who do not take enough calcium and vitamin D with their diet are more at risk of developing the disease. Finally, hyperparathyroidism more frequently affects people with multiple endocrine neoplasia (a rare hereditary disease), those who underwent radiation treatment in the neck area, and individuals on lithium therapy (a drug often used in the treatment of bipolar disorder).