Disorders of calcium metabolism on the USMLE Step 1 exam

Tyler York

Imbalances in calcium metabolism result in hypercalcemia and hypocalcemia. Diseases affecting the parathyroid gland, kidneys and liver are the major causes of calcium imbalances. Levels of parathyroid hormone or PTH, calcium and phosphate can help to diagnose the cause of hypercalcemia and hypocalcemia.

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Full Disorders of calcium metabolism on the USMLE Step 1 exam video transcript:

Hello everyone, I am to Jetta in this video, I would like to talk about disorders of calcium metabolism. Calcium levels in your body are regulated mainly by the effects of parathyroid hormone or pdh vitamin D and to a small extent by calcitonin disorders in calcium metabolism, Millie to hypercalcemia or hypocalcemia.

Causes of hypercalcemia include hyperparathyroidism vitamin D toxicity. Paraneoplastic syndrome is due to excess pth related peptide situation, some other malignancies and medications. Like he has AIDS estrogens, Etc,

Hyperparathyroidism is one of the most common causes of hypercalcemia. It is simply excess pdh in the body. Depending upon what is the primary issue, causing the excess. Pdh hyperparathyroidism can be divided into three types, primary secondary and tertiary hyperparathyroidism

Hyperparathyroidism maybe primary secondary or tertiary in primary hyperparathyroidism, the defect is in the parathyroid gland. For example, if maybe a parathyroid adenoma or it may be better, Tyler Glenn hypertrophy. Sometimes it may be caused due to lithium toxicity in secondary hyperparathyroidism the cause is outside the parathyroid gland more. Commonly it may be a chronic renal failure which causes vitamin D deficiency or it may be a primary vitamin D deficiency or a low calcium intake. Hyperparathyroidism is seen. Most commonly in long-standing cases of chronic renal failure.

The clinical features of hyperparathyroidism are due to the effects of hypercalcemia it may present with abdominal pain, constipation renal calculi. I take on mental changes anxiety, mood changes, or some special surprise fake features like calciphylaxis and osteitis fibrosa cystica. If Alexis is a condition, which is caused by clotting in the subcutaneous tissues of the body due to activation of clotting and Signs by the excess calcium. In the blood, on the other hand, osteitis, fibrosa cystica is a bone condition. Also, call Les Brown, tumors, it is not a malignant or premalignant condition that occurs due to collection of hemorrhagic fluid within the bone which is being lionized due to the extra pdh in the body.

Let's look at the laboratory features in hyperparathyroidism. So while investigating hyperparathyroidism, we need to look at the levels of pdh serum calcium and phosphate. So irrespective of the cause in all cases of hyperparathyroidism, the pth in serum, will always be elevated. So we are going to differentiate primary secondary and tertiary hyperparathyroidism by the serum calcium and serum phosphate levels.

In primary hyperparathyroidism is going to be high which causes the serum calcium to be high and the serum phosphate to be low. So this is just a result of the excess pth on the other hand in secondary. Hyperparathyroidism, the primary cause is a low serum calcium level which in turn will cause the PTA to be elevated. To the level of phosphate will actually depend on what is the cause of secondary hyperparathyroidism. If the causes renal failure than the phosphate will be elevated, if the cause is vitamin D deficiency, then the serum phosphate is going to be low. On the other hand, in tertiary, hyperparathyroidism the elevated serum, calcium is more likely to be normal. The serum phosphate is more likely to be normal or sometimes it may be high depending again on the cause

Some of the common causes of hypocalcemia include hypoparathyroidism malnourishment vitamin D deficiency, or vitamin D with scepter deficits, chronic liver disease, chronic kidney disease, certain medications like a matinee by phosphonate and disorders in magnesium.

The clinical features of hypocalcemia include fatigue. Tetany paraesthesias, muscle cramps. And some mental changes. They may be basal ganglia calcifications, especially in primary hyperparathyroidism elevated. Some of the clinical signs that can be elicited is chvostek sign and Coastline. Most exciting is elicited by tapping. The facial nerve which causes facial twitching and paraesthesia in the distribution of the facial nerve. A sign is elevated by inflating, a blood pressure cuff in the middle arm which then results in carpopedal. Spasm

There are three types of hypoparathyroidism the most common is primary hyperparathyroidism followed by pseudohypoparathyroidism. And the last one, which is pseudopseudohypoparathyroidism. The most common cause of primary hyperparathyroidism is iatrogenic. That is surgical excision of the parathyroid gland while doing thyroid surgery, like a lobectomy or a partial thyroidectomy. Sometimes it may follow irradiation to the neck and thyroid gland. Sometimes it may be a part of poly glandular autoimmune syndromes or it may be due to metastasis to the parathyroid gland which may stop the functioning of the parathyroid glands. Etc conditions, especially DiGeorge syndrome, can also be associated with primary hyperparathyroidism include low pth level, which will then lead to

Low calcium and a high serum phosphate level.

Pseudohypoparathyroidism is also called as a bright Herda, Terry, osteodystrophy, it is caused by a receptor, defect of pth. There is no problem in the parathyroid gland. The problem is in the receptor where are parathyroid hormone acts at the tissue level. So what happens is, the mutation is inherited from the mom in this case and it leads to mental retardation and short, fourth and fifth metacarpal bones, which can be seen clinically or on x-ray of the hand.

In pseudopseudohypoparathyroidism, it is an autosomal dominant disorder. That is inherited from the father and it shows mutations in the gene has Gene. There is no resistance to the effect of pth in comparison to pseudohypoparathyroidism disabilities. A short 4th or 5th, metacarpal, bone, just like in pseudohypoparathyroidism around or moon face and shot station in both types. Of pseudohypoparathyroidism May Show, varying levels of pH, serum, calcium, and serum. Phosphate more often the pth is normal or high rather than the serum calcium is normal or it may be loved and the same phosphate is more likely to be elevated.

Hold this video, clarify some of your Concepts on hypercalcemia hypocalcemia and disorders of calcium metabolism. Thanks for watching.
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