1. Parathyroid Glands
HUSSEN.S.ALNAKHLY

2. PARATHYROID GLAND
Location:
Usually paired.
Very small (less than 5 mm).
Called parathyroid glands because of their position on posterior margins outer surface of thyroid gland.
More superior of each pair usually near middle of margin of lobe.
More inferior of each pair usually at inferior apex of lobe.
Development: Like thyroid gland, develop from endodermal thickening in floor of early pharynx and epithelium of 3rd and 4th gill slit pouches.

4. Anatomy Arterial supply usually from inferior thyroid art
Superior glands usually imbedded in fat on posterior surface of middle or upper portion of thyroid lobe
Lower glands near the lower pole of thyroid gland
In 1-5% pts, inferior gland in deep mediastinum

5. Histology 50/50 parenchymal cells, stromal fat
Chief cells – secrete PTH
Waterclear cells
Oxyphil cells

6. Parathyroid Hormone
Synthesized in chief cells as large precursor – pre-proparathyroid hormone
Cleaved intracellularly into proparathyroid hormone then to final 84 AA PTH
PTH then metabolized by liver into hormonally active N-term and inactive C-term

7. PTH function

8. Hyperparathyroidism Primary Hyperparathyroidism
Normal feedback of Ca disturbed, causing increased production of PTH
Secondary Hyperparathyroidism
Defect in mineral homeostasis leading to a compensatory increase in parathyroid gland function

9. Etiology Unknown cause Single gland adenomatous disease
Multiglandular disease – exogenous stimulus
Ionizing radiation exposure

10. Clinical Presentation
Nephrolithiasis
Bone Disease
Peptic Ulcer Disease
Psychiatric disorders
Muscle weakness
Constipation
Polyuria
Pancreatitis
Myalgia
Arthralgia

11. Hypercalcemia Hyperparathyroidism (most common)
Malignancy (most common in hospitalized)
Lytic metastases to bone
PTHrP producer
Sarcoidosis / granulomatous disease
Vit D intoxication
Thiazides
Hyperthyroidism
Familial hypocalciuric hypercalcemia

12. Renal Complications Generally the most severe clinical manifestations
Many have frequency, polyuria, polydipsia
Usually present w/ nephrolithiasis (20-30%)
Calcium phosphate or Calcium oxalate
Nephrocalcinosis (in 5-10%) – calcification w/in parenchyma of kidneys
Severe renal damage
Hypertension secondary to renal impairment

13. Bone Disease Osteitis fibrosa cystica
In early descripts of disease, many had severe bone disease (50-90%), but now 5-15%
Subperiosteal resorption – pathognomonic of hyperparathyroidism

16. Gastrointestinal Manifestations
Peptic Ulcer disease
Pancreatitis
Cholelithiasis – 25-35%

17. Neuromuscular complications
Muscular weakness, fatigue
More commonly in proximal muscles
Sensory abnormalities also possible

18. Laboratory Diagnosis Elevated Serum Ca and PTH
Must measure Ionized Ca (subtle cases of hyperPTH will have normal Serum Ca)
50% will have hypophosphatemia Elevated Alkaline Phosphatase in 10-40%
Hyperchloremic metabolic acidosis
Low Mg in 5-10%
High Urinary Ca in almost all cases