Question:
The year is 2020. You are a postdoc currently working on a randomized control trial evaluating the influence of whole fat vs. low fat dairy products on cardiometabolic risk factors. Part of your analysis includes a blood test for a variety of compounds (e.g., minerals and hormones). As you sift through the data, you come across an unusual result: one subject has abnormally high calcium plasma levels. Upon further investigation, you find that their parathyroid hormone (PTH) plasma levels are also elevated. Something doesn’t seem right! Suddenly, a wave of nostalgia passes over you. It’s been years since you have taken nutritional biochemistry, but you vaguely remember a lecture on calcium. Before the information slips your mind, you …show more content…
Calcium sensing involves the binding of calcium to calcium-sensing receptors (CasR), which, depending on the location (e.g., parathyroid glands, skin, kidney, or bones), elicit a change in metabolism through intracellular signaling. When extracellular calcium levels are high, CasR binding inhibits PTH transcription through intracellular transduction pathways in the parathyroid glands. Consequently, PTH secretion and blood levels decrease. In contrast, when calcium levels are low, PTH is upregulated and secretion from the parathyroid glands increases. In terms of calcium homeostasis, the regulation of PTH by calcium-sensing is important because PTH influences calcium flux in several …show more content…
The process of reabsorption in the kidneys involves the proximal tubule (passive; 1,25(OH)2D-independent) and distal tubule (active; 1,25(OH)2D-independent). Depending on calcium status, the kidneys are capable of reabsorbing 98% of the calcium that is filtered through proximal and distal tubule. In the distal tubule, 1,25(OH)2D and PTH regulate calcium reabsorption through an active mechanism that is very similar to the calcium absorption mechanism in the intestinal cells. When calcium levels are low, secretion of phosphate is increased and calcium absorption is increased. In contrast, when calcium levels are high, PTH stimulates calcium reabsorption and the urinary excretion of
The year is 2020. You are a postdoc currently working on a randomized control trial evaluating the influence of whole fat vs. low fat dairy products on cardiometabolic risk factors. Part of your analysis includes a blood test for a variety of compounds (e.g., minerals and hormones). As you sift through the data, you come across an unusual result: one subject has abnormally high calcium plasma levels. Upon further investigation, you find that their parathyroid hormone (PTH) plasma levels are also elevated. Something doesn’t seem right! Suddenly, a wave of nostalgia passes over you. It’s been years since you have taken nutritional biochemistry, but you vaguely remember a lecture on calcium. Before the information slips your mind, you …show more content…
Calcium sensing involves the binding of calcium to calcium-sensing receptors (CasR), which, depending on the location (e.g., parathyroid glands, skin, kidney, or bones), elicit a change in metabolism through intracellular signaling. When extracellular calcium levels are high, CasR binding inhibits PTH transcription through intracellular transduction pathways in the parathyroid glands. Consequently, PTH secretion and blood levels decrease. In contrast, when calcium levels are low, PTH is upregulated and secretion from the parathyroid glands increases. In terms of calcium homeostasis, the regulation of PTH by calcium-sensing is important because PTH influences calcium flux in several …show more content…
The process of reabsorption in the kidneys involves the proximal tubule (passive; 1,25(OH)2D-independent) and distal tubule (active; 1,25(OH)2D-independent). Depending on calcium status, the kidneys are capable of reabsorbing 98% of the calcium that is filtered through proximal and distal tubule. In the distal tubule, 1,25(OH)2D and PTH regulate calcium reabsorption through an active mechanism that is very similar to the calcium absorption mechanism in the intestinal cells. When calcium levels are low, secretion of phosphate is increased and calcium absorption is increased. In contrast, when calcium levels are high, PTH stimulates calcium reabsorption and the urinary excretion of