Bone and Parathyroid Flashcards
What is Parathyroid Hormone (PTH)?
A hormone secreted from four parathyroid glands that regulates calcium levels in the body
PTH responds to calcium levels by increasing or decreasing its secretion
Where are the parathyroid glands located?
Adjacent to the thyroid gland
They are four small glands that play a crucial role in calcium regulation
What are the primary actions of PTH in the bone?
Increases resorption of calcium from the bone
This process can lead to weaker bones if excessive
How does PTH affect the kidneys?
Increases calcium reabsorption and phosphate excretion
It also enhances the hydroxylation of Vitamin D
What is the role of Vitamin D in calcium absorption?
Promotes dietary absorption of calcium in the intestines
Vitamin D is activated in the liver and kidneys
What is free calcium also known as?
Ionized calcium
It is the biologically active form of calcium in the body
What can excessive resorption of calcium lead to in bones?
Osteoporosis
This condition makes bones weaker and more prone to fractures
What can result from hypercalcemia?
Symptoms such as intellectual weariness, personality changes, nausea, and kidney stones
Hypercalcemia is often due to primary hyperparathyroidism
What percentage of calcium in the body is found in bones?
99%
Only 1% circulates in blood and other fluids
What is the primary cause of hypocalcemia?
Decreased PTH, Vitamin D deficiency, or malabsorption
Low albumin levels and low magnesium can also contribute
What is the effect of low magnesium on PTH?
Inhibits secretion of PTH and impairs its action
Low magnesium levels can lead to vitamin D resistance
What is the reference range for total calcium in mmol/L?
2.24-2.53 mmol/L
This range is important for diagnosing calcium-related disorders
What is the role of phosphate in the body?
Participates in genetic material, coenzymes, and ATP reservoirs
Phosphate levels are regulated by the kidneys
What is hypophosphatemia commonly seen in?
Diabetic ketoacidosis (DKA), COPD, and alcoholism
It can result from shifts in phosphate into cells
What is the reference range for phosphate levels in adults?
0.81-1.45 mmol/L
Levels can vary by age and health status
True or False: Ionized calcium levels can be reliably calculated from total calcium in critically ill patients.
False
Ionized calcium may not be accurately reflected due to changes in binding
What is the relationship between PTH and vitamin D?
They work together to maintain calcium levels in the body
PTH increases calcium levels, while vitamin D enhances absorption
Fill in the blank: The predominant intracellular anion is _______.
Phosphate
Phosphate plays a critical role in cellular functions
What is the primary cause of hypermagnesemia?
Renal failure, especially with antacids or laxatives
It can occur in patients with heart problems
What is the role of magnesium in the body?
Essential cofactor to more than 300 enzymes
Magnesium is also important for cardiovascular and neuromuscular health
What is adjusted calcium and how is it calculated?
Adjusted Total Calcium (mmol/L) = Total calcium (mmol/L) + 0.02 [47 - Albumin (g/L)]
This calculation accounts for changes in albumin levels
What happens to ionized calcium at low pH?
Increases in ionized calcium
More H+ ions lead to less calcium binding to albumin
What is the significance of ionized calcium in critically ill patients?
It reflects the active form of calcium, which is crucial for physiological functions
Total calcium may not accurately represent the patient’s condition
