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Phase 2a - Endocrinology > PTH > Flashcards

PTH Flashcards

1
Q

Actions of PTH

A
  • Increased calcium reabsorption
  • Decreased phosphate reabsorption
  • Increased 1-alpha-hydroxylation of 25-OH vit D
  • Increased bone remodelling
  • Bone resorption > bone formation
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2
Q

PTH has no direct effect on what

A
  • Intestines
    But increased calcium absorption because of increased 1,25 (OH)2 vit D
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3
Q

Calcium homeostasis is an example of what?

A

Negative feedback

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4
Q

Why is calcium important?

A

Functioning of nerves and muscles

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5
Q

Appropriate changes in PTH

A

Maintain calcium balance

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6
Q

Inappropriate changes in PTH

A

Cause calcium imbalance

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7
Q

How is corrected calcium calculated?

A

Corrected calcium =
total serum calcium + 0.02 * (40-serum albumin).

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8
Q

What are the consequences of hypocalcaemia?

A

Parasthesia
Muscle spasm (hands and feet, larynx, premature labour)
Seizures
Basal ganglia calcification
Cataracts
ECG abnormalities (long QT)

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9
Q

Chvostek’s sign

A

Tap over the facial nerve and look for spasm of facial muscles.

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10
Q

Trousseau’s sign

A

Inflate the blood pressure cuff to 20mm Hg above systolic for 5 mins.

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11
Q

Causes of hypocalcaemia

A

Vitamin D deficiency (increased calcium absorption in the intestines)

Hypoparathyroidism (due to surgery or radiation).

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12
Q

Hypoparathyroidism due to syndromes

A

Di George
o HDR
o Kenney-Caffey
o Sanjad –Sakati
o Kearns-Sayre
o Blomstrand chondrodysplasia

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13
Q

Di George syndrome

A

Developmental abnormality of third and fourth branchial pouches.

Hypoparathyroidism
Thymic aplasia
Immunodeficiency
Cardiac defects
Cleft palate
Abnormal facies

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14
Q

Genetic causes of hypoparathyroidism

A

Recessive
Dominant
X-linked

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15
Q

Autoimmune causes of hypoparathryoidism

A

Isolated
Polyglandular type 1
(chronic mucocutaneous candidiasis, hypoparathyroidism, autoimmune adrenal insufficiency).

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16
Q

Hypoparathyroidism due to infiltration

A

Haemochromatosis
Wilson’s disease

Metal accummulation.

17
Q

Hypoparathyroidism can also occur due to deficiency in what?

A

Magnesium (PTH in vesicle which needs to be trafficked to cell surface ← this required magnesium (hypomagnesaemia due to alcohol etc).

18
Q

Decreased PTH leads to

A

Decreased renal calcium reabsorption > increased relative calcium excretion.

Increased renal phosphate reabsorption > increased serum phosphate > Decreased formation of 1,25 (OH2) D

Decreased bone resorption.

Decreased intestinal calcium absorption.

DECREASED SERUM CALCIUM!

19
Q

Pseudohypoparathyroidism

A

Resistance to PTH (Type 1 Albright hereditary osteodystrophy - mutation with deficient Galpha subunit).

  • Short stature
  • Obesity
  • Round facies
  • Mild learning difficulties
  • Subcutaneous ossification
  • Short fourth metacarpals
  • Other hormone resistance
20
Q

What are non-primary causes of hypercalcaemia?

A

Tourniquet on for too long.

Blood sample is old and haemolysed.

21
Q

What are the symptoms of hypercalcaemia?

A

Thirst, polyuria
Nausea
Constipation

22
Q

What are the consequences of hypercalcaemia?

A

Confusion and coma
Renal stones
ECG abnormalities (short QT)

23
Q

Causes of hypercalcaemia?

A

90% of cases:
Malignancy
- bone mets, myeloma, PTHrP, lymphoma
- Primary hyperparathyroidism

  • Thiazides
  • Thyrotoxocosis
  • Sarcoidosis
  • Familial hypocalciuric / benign hypercalcaemia
  • Immobilisation
  • Milk-alkali
  • Adrenal insufficiency
  • Phaeochromocytoma
24
Q

What are the consequences of primary hyperparathyroidism?

A

Bones:
- osteitis fibrosa cystica (skull cysts)
- osteoporosis (sub-periosteal erosion of the phalanges)

Stones:
- kidney stones

Groans:
- psychic - confusion

Moans:
- abdominal
- constipation
- acute pancreatitis

25
Q

80% of primary hyperparathyroidism is caused by what?

A

Single benign adenoma.

26
Q

15-20% of primary hyperparathyroidism is caused by what?

A

Four gland hyperplasia.
MEN I or II

27
Q

What percent of primary hyperparathyroid tumours are malignant?

A

<0.5%

28
Q

How does the blood panel look in vit. D deficiency?

A

PTH: high
Calcium: low
Phosphate: low
Appropriate

29
Q

How does the blood panel look in hypoparathyroidism?

A

PTH: low
Calcium: low
Phosphate: high
Inappropriate

30
Q

How does the blood panel look in pseudohypoparathyroidism?

A

PTH: high
Calcium: low
Phosphate: high
Appropriate

31
Q

How does the blood panel look in hypercalcaemia of malignancy?

A

PTH: low
Calcium: high
Phosphate: - (can be any)
Appropriate

32
Q

How does the blood panel look in primary hyperparathyroidism?

A

PTH: high
Calcium: high
Phosphate: low
Inappropriate

Phase 2a - Endocrinology (11 decks)

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