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Parathyroid Glands Physiology

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Title: Parathyroid Glands Physiology


1
Parathyroid Glands Physiology
  • Dr Taha Sadig Ahmed

2
  • Four glands located on the posterior surface of
    the thyroid gland
  • Secrete the polypeptide hormone PTH
  • Decreased blood level of Ca ? stimulates the
    Parathyroids to secrete PTH

3
Regulation of PTH secretion
  • Secretion of PTH is inversely related to plasma
    Ca2 because ?
  • Plasma Ca2 level is the dominant regulator of
    PTH secretion
  • Plasma Ca2 level lt 3.5 mg/dL ? stimulates PTH
    secretion
  • Plasmna Ca2 level gt 5.5 mg/dL ? inhibits PTH
    secretion

4
Effects of PTH
Increase blood Ca Decrease blood Phosphate
5
Effects of PTH
6
(No Transcript)
7
Hypoparathyroidism
  • Causes ?
  • (1) Abnormal parathyroid gland ?Reduced or absent
    synthesis of PTH
  • (2) Inadvertent (by mistake) removal of
    parathyroid gland during thyroid surgery
  • This may lead to Tetany (increased excitability
    hypersensitivity of nerves and muscles ) .
  • Hypoparathyroidism is associated with
    hypocalcemia , but hypocalacemia can also
    accompany severe Vit D deficiency .

8
Signs Symptoms of Hypoparathyroidism
  • Positive Chvosteks (facial muscle twitch) sign
  • Positive Trousseaus (carpal spasm) sign
  • Delayed cardiac repolarization with prolongation
    of the QT interval
  • Paresthesia
  • Tetany

9
HYPO PARATHYROIDISM
  • Tetany can be overt???? or latent??? ?????
    ??????? ???????
  • ????? ???????? ???
  • Chorosteks sign Tapping the facial nerve as it
    emerge from the parotid gland in front of the
  • ear ? causes contraction of facial muscles.
  • Trousseaus sign
  • Arresting (stopping ) blood flow to the forearm
    for fe minutes ( e.g., by sphygmomanometer ) ?
    causes flexion at the wrist, thumb and
    metacarpophalangeal joints.

10
Carpopedal spasm sign of tetany
11
Hyperparathyroidism
  • Adenoma ( tumor ) of parathyroid gland ?
    excessive PTH secretion
  • Hypercalcemia results from combined effects of
    increased
  • (1) bone resorption, and
  • (2) intestinal and reanal calcium absorption

12
Features of Hyperparathyroidism
  • Kidney polyuria , polydipsia , renal stones
  • Bones Rickets or osteomalacia , osteitis
    fibrosa cystica ( soft bones with cyst formation
    in picture arrows point to cysts )
  • GIT nausea , vomiting , indigestion ,
    constipation , pepticulcer , pancreatitis
  • Musculoskeletal proximal muscle weakness
  • CNS depression , memory loss , psychosis ,
    coma

13
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