Please enable JavaScript.
Coggle requires JavaScript to display documents.
Disorders of Calcium Metabolism (clean-up) - Coggle Diagram
Disorders of Calcium Metabolism (clean-up)
Organs regulating calcium & phosphate:
Hormones regulating calcium: Parathyroid Hormone
Parathyroid Glands
Hyperparathyroidism (Primary)
Hypercalcemia
Increased PTH levels
Hypoparathyroidism
Decreased PTH levels
Hypocalcemia
Maintain serum ionized calcium concentration within very narrow limits
Only endocrine product of the parathyroid gland is parathyroid hormone (PTH)
Inverse relationship between ionized calcium concentration and PTH in the blood Actions
Skeleton:
Increases osteoclastic activity
Mobilizes Ca++ and P from bone to blood
Kidneys:
PTH increases calcium, but reduces phosphate levels
↑ Reabsorption of Ca++
↓ Reabsorption of Phosphorus
Intestines:
↑ intestinal absorp on of calcium and phosphorous
PTH + Calcitriol ‐ act synergistically (1° calcitriol effect)
GI tract
Bone
Kidneys
Calcium in the Body
Calcium & phosphorus absorbed from the gut
Deposition in (& release from) bones
Excretion by the kidneys
Calcium: Filtration & tubular reabsorption
Phosphorus: Filtration & tubular reabsorption
How Calcium Lives in Blood
Serum Total Calcium composed of 3 forms:
Protein‐bound (albumin)
Complexed (with anions)
Ionized (metabolically active)
Factors that may influence blood calcium:
Serum albumin
Acid‐base
Acidemia – increases Ca++
Alkalemia – decreases Ca++ Key Points to Know About Calcium
Calcitonin
As CA++ increases to high normal, PTH declines and calcitonin is released from the thyroid gland to prevent hypercalcemia.
Calcitonin ↓ blood Ca2+ levels:
Inhibits intestinal CA2+ absorption
Inhibits osteoclast & stimulates osteoblast activity
Inhibits renal reabsorption of Ca2+ and phosphorus
Calcitriol
Primary action: ↑ gut Ca absorp on
Facilitates PTH action on bone by promoting osteoclast formation
Stimulates re‐absorption of calcium and phosphorus by kidneys
Inhibits synthesis & storage of PTH
Interpreting common diagnostics
Calcium Panel
Consists of:
Ionized calcium concentration
PTH activity
Parathyroid related protein (PTHrP)
always assess serum calcium relative to serum:
Albumin concentrations ‐ bound
Urea nitrogen concentrations ‐ renal
Creatinine concentrations ‐ renal
Phosphorus concentrations – PTH vs Vit D
Mean total Ca+2 = 15.6 mg/dl ( 12.1‐23 mg/dl)
Hypercalcemia tends to be:
Stable and fluctuate little day to day
Typically increases over time (weeks to months)
serum Phosphorus usually low to low normal
Typical [PO4] = 3.1 mg/dl
High PTH promotes renal excretion of Phosphorus
Value of Serum Phosphorous
Hypercalcemia with normal to low phosphorous and normal renal values:
Primary HyperPTHism (P usually low)
Hypercalcemia of malignancy (P usually normal)
Hypercalcemia with hyperphosphatemia:
Vitamin D toxicity
Renal causes
Osteolysis Interpreting PTH Values
PTH is evaluated in light of the total serum +2 calcium or preferably, the ionized [Ca ]
With primary 1⁰HPTHism
PTH values range from high normal to elevated (N = 4‐45 pmol/L)
CKD
PTH values much higher than with 1⁰HPTHism
ionized [Ca+2] is typically normal or low.
if low, Renal Secondary Hyperparathyroidism
Thoracic Radiographs & Abdominal Ultrasound
diagnosis of occult hypercalcemia.
Screens for non‐palpable abdominal tumors and asymptomatic thoracic tumors
Medical Management of Hypercalcemia
Correct dehydration
Saline diuresis (calciuresis) 1.5‐2 x maintenance
Diuretics (Furosemide) 5 mg/kg/IV q12‐24 hrs after correcting dehydration
Mild alkalinization (3 meq/kg/IV over 30‐60 min)
Effects may last for 3 hrs or more
Calcitonin; 4‐5 units/kg q8‐12 hrs SQ
Panidronate disodium (a bisphosphonate) 1.3 mg/kg SID to BID IV in saline. $$$$ Alternatives to Surgery?
Ultrasound guided:
Heat ablation (similar to surgical success)
Ethanol ablation (less successful)
Higher complication rates than surgery
Laryngeal paralysis
Horner’s syndrome
Prognosis
Excellent if appropriate dosages of vitamin D are provided and iatrogenic renal failure is prevented
Rechecks at one to 3 month intervals will prevent serious hypercalcemia from going undetected
Hypercalcemia: clinical signs