[09.06] Common Bone and Mineral Disorders V2.pdf

Mobility, protection of internal organs, and reservoir for ions

What are the three primary mechanical and storage functions of bone?

Hematopoiesis

Which process does the bone marrow host and regulate?

Bone remodeling

What is the dynamic process where old bone is constantly broken down and replaced by new bone?

Repair microdamage and maintain serum calcium

What are the two primary reasons for bone remodeling?

3 weeks

Approximately how long does it take for bone breakdown to occur during remodeling?

3 months

Approximately how long does it take to build bone back up during remodeling?

Basic multicellular unit BMU

What is the term for the functional unit consisting of osteoclasts and osteoblasts involved in remodeling?

Osteoclast

Which cell type is responsible for creating a resorption pit and chewing up bone?

Osteoid

What is the term for unmineralized bone laid down by osteoblasts?

Calcium, magnesium, and phosphorus

Which three minerals must be incorporated into the osteoid for it to become mineralized bone?

Bone turnover

What is the term for the rate at which bone remodels?

Primary hyperparathyroidism

Which condition is associated with accelerated bone turnover?

Adynamic bone disease

What type of bone disease in chronic kidney disease is characterized by hardly any turnover?

Vitamins A, D, E, and K

Name the four fat-soluble vitamins.

Vitamin D

Which vitamin is the exception to the rule that vitamins cannot be synthesized by humans?

10 AM to 2 PM

During what time window is Vitamin D most effectively made in the skin?

65 percent

Calcium and phosphorus together make up what percentage of bone weight?

99 percent

What percentage of total body calcium is stored in the bone?

1 percent

What percentage of body calcium is metabolically active in the blood?

Albumin

45 percent of plasma calcium is typically bound to which protein?

40 percent

What percentage of plasma calcium exists in a free or ionized state?

0.8 mg/dL

For every 1g/dL of albumin above or below 4g/dL, total calcium concentration changes by approximately how much?

8.5 to 10.5 mg/dL

What is the general reference range for serum calcium?

Corrected calcium

What must be calculated if a patient has abnormal albumin levels and you need an accurate calcium reading?

Ionized calcium

Which measurement of calcium is more expensive and can be affected by acid-base disorders?

Decreased ionized calcium

What is the effect of an alkaline pH (increased pH) on ionized calcium levels?

Increased ionized calcium

What is the effect of an acidic pH (decreased pH) on ionized calcium levels?

21 days

Approximately how long is albumin relatively stable in the blood?

Reference range

What is the preferred term to use instead of "normal" when quoting lab values?

Parathyroid hormone PTH

What is the "master hormone" for calcium regulation?

Chief cells

Which specific cells of the parathyroid gland excrete PTH?

Behind the thyroid gland

Where are the parathyroid glands typically located?

Grain of rice

How is the size of a parathyroid gland typically described?

4 minutes

What is the half-life of PTH?

Ionized calcium concentration

What is the major regulator of PTH secretion?

Calcium sensing receptor CaSR

What receptor on the parathyroid gland does ionized calcium bind to?

Inhibition of PTH secretion

What happens to PTH secretion when the CaSR is activated by high calcium?

C cells

Which cells in the thyroid gland produce calcitonin?

Neural crest

From which embryonic tissue are C cells derived?

Somatostatin

Which hormone, also secreted by C cells, inhibits calcitonin?

Decreases tubular reabsorption

What is the effect of calcitonin on calcium in the kidney?

Impairs osteoclast absorption

How does calcitonin affect bone?

Medullary thyroid carcinoma

Calcitonin is used as a tumor marker for which neuroendocrine disease?

Calcitonin

Which hormone enables calcium deposition in bones instead of bone release?

Stimulate osteoclast resorption

How does PTH affect bones to increase calcium levels?

Stimulate calcium reabsorption

How does PTH affect the kidneys to maintain calcium?

1-alpha-hydroxylase

Which kidney enzyme is stimulated by PTH to activate Vitamin D?

25-hydroxyvitamin D

What is the circulating, biologically inactive form of Vitamin D?

Calcitriol or 1,25-dihydroxyvitamin D

What is the active form of Vitamin D called?

Small intestine

Where does calcitriol primarily stimulate the absorption of calcium and phosphorus?

Dermal synthesis

What is the major natural source of Vitamin D?

7-Dehydrocholesterol 7-DHC

Which substance in the skin becomes Previtamin D3 when exposed to UV light?

10 to 15 minutes

How much midday sunlight exposure of hands, arms, and face 2 to 3 times per week is recommended?

Clothing, sunscreen, and pollution

Name three factors that reduce the amount of Vitamin D made in the skin.

Liver

Where is Vitamin D first converted into its major circulating form?

Kidney

In which organ is Vitamin D converted into its active steroid hormone form?

Breastfed infants, older patients, and dark skin

Name three groups at high risk for Vitamin D deficiency.

Obese patients

Which group of patients sequesters more Vitamin D in subcutaneous fat, altering its release?

Rickets

What condition results from insufficient Vitamin D in children?

Osteomalacia

What condition results from insufficient Vitamin D in adults?

Delayed closure of fontanelles

Name a clinical feature of rickets related to the skull.

Rachitic rosary

What is the term for the bead-like bumps on the ribs in rickets?

Bowing of legs

What is the characteristic limb deformity in rickets?

High intake of supplements

What is the primary cause of Vitamin D toxicity?

Vascular and tissue calcification

What is a serious consequence of Vitamin D toxicity besides arrhythmias?

85 percent

What percentage of the body's phosphorus is found in the bone?

Phosphate PO4

In what chemical form does plasma phosphorus primarily exist?

Phosphatonin

What is the descriptive term for hormones like PTH that cause the excretion of phosphorus?

Increased urinary excretion

How does PTH respond to elevated phosphorus levels?

Decreased

Should 1-alpha-hydroxylase be increased or decreased when phosphorus levels are high?

Fibroblast Growth Factor 23 FGF23

What is the key regulator of phosphorus homeostasis expressed in bone?

Klotho

Which co-receptor is required for FGF23 to function?

Osteoblasts and osteocytes

Which cells primarily secrete FGF23?

Stimulate renal phosphorus excretion

What is the short-term physiological role of FGF23?

Limit intestinal absorption

What is the long-term physiological role of FGF23?

Hyperparathyroidism

What condition is characterized by excess PTH?

Primary hyperparathyroidism

What is the most common cause of asymptomatic hypercalcemia?

Parathyroid adenoma

A single one of these causes 80 percent of primary hyperparathyroidism cases?

Nephrolithiasis

In which type of patient might you suspect primary hyperparathyroidism if they have kidney stones?

Symptomatic, Asymptomatic, and Normocalcemic

What are the three phenotypes of primary hyperparathyroidism?

High PTH and normal calcium

What are the lab findings in normocalcemic hyperparathyroidism?

Ultrasonography, Sestamibi scan, and 4D CT

Name three preoperative localization methods for parathyroid tissue.

Drop of more than 50 percent

What intraoperative change in PTH concentration indicates a successful removal of an adenoma?

Arrhythmias, hypertension, and heart attack

Since patients don't die from high calcium, what complications do they die from?

Cinacalcet

Which calcimimetic agent binds to the CaSR to reduce PTH synthesis?

Secondary hyperparathyroidism

Which condition is a response of the glands to hypocalcemia or Vitamin D deficiency?

Chronic renal failure

What is a classic condition associated with secondary hyperparathyroidism?

Elevation of PTH

What metabolic change begins early in the course of chronic kidney disease, even before creatinine rises?

Low calcium, high phosphate, high PTH, and inactivated Vitamin D

What four biochemical abnormalities characterize CKD Mineral and Bone Disorder?

Vascular calcification, bone disease, and gland hyperplasia

What are the three clinical impacts of CKD-MBD?

Dietary phosphate restriction

What is the primary treatment for hyperphosphatemia in CKD?

Non-calcium phosphate binders

What type of binder is Sevelamer?

Tertiary hyperparathyroidism

What occurs when parathyroid glands become autonomous after prolonged secondary hyperparathyroidism?

Renal transplantation

Tertiary hyperparathyroidism is most commonly identified after which procedure?

Altered set point of the CaSR

What physiological change allows PTH to be secreted despite high calcium in tertiary hyperparathyroidism?

Malignancy

Besides primary hyperparathyroidism, what is the other most common cause of hypercalcemia?

Tuberculosis

Which granulomatous disease is a notable cause of hypercalcemia in the Philippines?

Moans, groans, stones, and psychotic overtones

What is the classic mnemonic for the symptoms of hypercalcemia?

Bones and joints

In the hypercalcemia mnemonic, what do "moans" represent?

Psychiatric/CNS problems

In the hypercalcemia mnemonic, what do "psychotic overtones" represent?