GENERAL HISTOLOGY

Detailed explanation-1: -∎ As kidney disease gets worse and blood vitamin D levels decrease, the body makes more and more parathyroid hormone (PTH), causing secondary hyperparathyroidism (SHPT). ∎ When SHPT is present there are low blood levels of vitamin D and calcium and high blood levels of PTH and phosphate.

Detailed explanation-2: -Vitamin D is necessary to absorb dietary calcium from the gut. In vitamin D deficiency, less calcium from food is absorbed in the gut, so blood calcium levels are low and this causes more parathyroid hormone to be produced.

Detailed explanation-3: -Defect in the activation of vitamin D in the kidneys due to chronic kidney disease (CKD) leads to hypocalcemia and hyperphosphatemia, resulting in a compensatory increase in parathyroid gland cellularity and parathyroid hormone production and causing secondary hyperparathyroidism (SHP).

Detailed explanation-4: -With chronic kidney disease, low vitamin D levels can be found, sometimes even severely low levels. This may occur because injured kidneys are less able to convert vitamin D into its active form.

Detailed explanation-5: -Chronic kidney failure is the most common cause of secondary hyperparathyroidism. In some people with long-term secondary hyperparathyroidism, usually from end-stage kidney disease, the parathyroid glands enlarge.