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1. Anatomy
2. Microbiology
3. Physiology
4. Pathology
4.1 General pathology
4.2 Central and peripheral nervous system
4.3 Cardiovascular system
4.4 Respiratory system
4.5 Hematology and oncology
4.6 Gastrointestinal pathology
4.7 Renal, endocrine and reproductive system
4.7.1 Renal system
4.7.2 Diabetes mellitus
4.7.3 Diabetic symptoms
4.7.4 Metabolic syndrome or Syndrome X
4.7.5 Thyroid disorders
4.7.6 Hypothyroidism
4.7.7 Hyperthyroidism
4.7.8 Malignancies of the thyroid gland
4.7.9 Parathyroid disorders
4.7.10 Hypoparathyroidism
4.7.11 Adrenal disorders
4.7.12 Adrenal insufficiency
4.7.13 Cushing’s syndrome
4.7.14 Additional information
4.8 Musculoskeletal system
5. Pharmacology
6. Immunology
7. Biochemistry
8. Cell and molecular biology
9. Biostatistics and epidemiology
10. Genetics
11. Behavioral science
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4.7.10 Hypoparathyroidism
Achievable USMLE/1
4. Pathology
4.7. Renal, endocrine and reproductive system

Hypoparathyroidism

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It is a condition characterized by low PTH levels.

Types of hyperparathyroidism

Type: Primary

  • Features: Iatrogenic excision of parathyroid glands during surgery on the thyroid gland, larynx or neck; neck irradiation; autoimmune polyglandular syndrome (adrenal insufficiency); congenital defects like DiGeorge syndrome, CATCH 22 defect; iron or copper overload; hypo and hypermagnesemia; aluminium toxicity; amyloidosis, sarcoidosis, metastases
  • Laboratory findings: Low PTH, low serum calcium, high phosphate, low 1,25 dihydroxy vit D

Type: Pseudohypoparathyroidism (Albright’s hereditary osteodystrophy)

  • Features: Resistance to PTH due to PTH receptor defect; inherited AD; mental retardation, short fourth and fifth metacarpals (short pinky and ring fingers); short stature; GNAS mutations
  • Laboratory findings: Normal to high PTH, decreased serum calcium, high serum phosphate, decreased 1,25 dihydroxy Vit D, normal 25 hydroxy Vit D; mutation inherited from mother

Type: Pseudopseudohypoparathyroidism

  • Features: Inherited AD; GNAS gene mutations;absence of PTH resistance; short stature, round face, short fourth and fifth metacarpals (short pinky and ring fingers), advanced bone age; learning disabilities
  • Laboratory findings: Normal PTH, normal or decreased calcium, normal or increased phosphate; mutation inherited from father

Clinical presentation is of hypocalcemia that includes paresthesias, tetany, fatigue, irritability, mood swings, seizures, wheezing and muscle cramps. Symptoms are worse with hyperventilation. Chvostek and Trousseau signs are positive. Chvostek sign includes facial twitching, peripheral numbness and twitching on tapping the facial nerve. Trousseau sign includes carpal spasm on inflating a blood pressure cuff around the arm. Basal ganglia calcifications are seen in primary hypoparathyroidism. Parkinson’s like syndrome, cataracts and spastic paraplegia may be seen. ECG may show prolonged QTc.

Treatment is by correction of hypocalcemia by calcium and Vitamin D supplementation. Recombinant PTH can also be given, if available.

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