Term
| Metabolic Functions of PTH |
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Definition
Mobilizes calcium from bone
Increases renal tubular reabsorption of calcium, thereby conserving it
Promotes renal production of
1,25-(OH)2D3, which increases intestinal absorption of calcium
Lowers serum phosphate by enhancing phosphaturia |
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Term
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Definition
The clinically most important pathologic conditions affecting the parathyroids are related to their hyperfunction.
More than 90% of cases of hypercalcemia are due to hyperparathyroidism or cancer. |
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Term
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Definition
> 95% related to sporadic adenoma or hyperplasia
F > M
Adenoma 75 to 80%
Primary hyperplasia 10 to 15%
Carcinoma <5% |
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Term
| Hypercalcemia caused by cancer |
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Definition
PTH-related peptide is a calcium-mobilizing humoral factor produced by some solid tumors, such as
Squamous carcinoma of the lung
Renal cell carcinoma
Bladder carcinoma
Ovarian carcinoma |
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Term
| Clinical Course of Parathyroidism |
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Definition
Stone and Bone disease
Kidney stones (recurrent)
Osteitis fibrosa cystica, brown tumors
Formerly common
Only about 10% today
Weakness, easy fatigability
Affective dysfunctions
Asymptomatic
Diagnosis
Hypercalcemia and hypophosphatemia
Elevated levels of PTH |
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Term
| Secondary Hyperparathyroidism |
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Definition
Secondary hyperparathyroidism is caused by any condition associated with decreased serum ionized calcium
Chronic renal failure - most common
Vitamin D deficiency (osteomalacia)
Pseudohyperparathyroidism (rare) |
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Term
| Hyperparathyroidism in Renal Failure |
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Definition
Phosphate retention
Hyperphosphatemia depresses serum Ca
Compensatory hyperparathyroidism
Reduced synthesis of 1,25-(OH)2D3
Impairs GI absorption
May stimulate PTH secretion
Renal osteodystrophy and other manifestations are less severe than in primary hyperparathyroidism |
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Term
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Definition
Hypoparathyroidism may be defined as deficient secretion of PTH accompanied by hypocalcemia
Most cases are surgically induced by
Inadvertent removal of all glands
during thyroidectomy
mistaken for lymph nodes
Fewer than 4 glands present
Too much parathyroid removed (hyperplasia Rx)
Other causes are uncommon
Congenital absence
Autoimmune disease
Rare familial autosomal and metabolic syndromes |
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Term
| Clinical Manifestations of Hypoparathyroidism |
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Definition
Increased neuromuscular excitability
Mild manifestations of this include
Circum-oral numbness
Tingling of fingers and toes
More extreme cases may result in
Carpopedal spasms
Laryngeal stridor
Convulsions
Tetany – decreased ionized calcium
Mental changes
Irritability
Depression
Psychosis
Calcification of the lens - cataracts
Intracranial changes
Calcifications in basal ganglia
Parkinsonian-like syndrome
Abnormalities in cardiac conduction
Dental abnormalities |
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Term
| Diagnosis of Hypoparathyroidism |
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Definition
Suspected - hypocalcemia
Confirmed - PTH absent or very low |
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