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Week 128 - Endocrinology > Parathyroid > Flashcards

Parathyroid Flashcards

1
Q

What does Parathyroid Hormone (PTH) affect?

A

Calcium - increase

Phosphate - decrease

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2
Q

What controls PTH?

A

Calcium ions decrease

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3
Q

What does calcitonin affect?

A

Calcium - decrease

Phosphate - decrease

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4
Q

What do vitamin D metabolites affect?

A

Calcium - increase

Phosphate - increase

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5
Q

What controls calcitonin?

A

Calcium ions increase

Gastrin

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6
Q

What controls vitamin D metabolites?

A

Phosphate decrease

PTH increase

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7
Q

Which cells secrete PTH?

A

Chief cells of the parathyroid gland

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8
Q

What receptor activates the cells for secretion of PTH?

A

Calcium sensing receptor on chief cells

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9
Q

How does PTH work on chief cell receptors?

A

Enhances:

  • renal tubular calcium reabsorption
  • osteoclast mediated bone resorption
  • conversion of 25(OH) vit D to 1,25(OH) vit D3
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10
Q

Describe the relationship between PTH and plasma calcium.

A

PTH level at highest when plasma Calcium at lowest

PTH level at lowest when plasma Calcium at highest

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11
Q

What are the most common causes of hypercalcaemia?

A
  • Primary hyperparathyroidism

- Malignancy

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12
Q

What are some less common causes of hypercalcaemia?

A
  • Milk-alkali syndrome
  • Ingestion of foods containing Vitamin D, including cod liver oil/herbal medication
  • Granulomatous diseases, sarcoidosis
  • Thiazide diuretics
  • Familial benign hypocalciuric hypercalcemia
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13
Q

Rare causes of hypercalcaemia?

A
  • Lithium
  • Total parenteral nutrition
  • Oestrogens/antioestrogens, testosterone
  • Vitamin A toxicity
  • Foscarnet
  • Thyrotoxicosis
  • Pheochromocytoma
  • Adrenal insufficiency
  • Vasoactive intestinal polypeptide hormone producing tumours
  • Immobilisation
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14
Q

How does excess PTH affect serum?

A 
Increased calcium
Decreased phosphorus
Increased alkaline phosphatase
Increased Chloride
Decreased bicarbonate
Increased PTH
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15
Q

How does excess PTH affect urine?

A

Increased calcium
Increased phosphorous
Increased cyclic AMP

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16
Q

Define:

  • Primary hyperparathyroidism
  • Secondary hyperparathyroidism
  • Tertiary hyperparathyroidism
A

Primary hyperparathyroidism:
- Adenoma, hyperplasia, carcinoma

Secondary hyperparathyroidism:
- Compensatory, elevated PTH level secondary to hypocalcaemia with parathyroid gland hyperplasia

Tertiary hyperparathyroidism:
- Autonomous secretion of PTH following
longterm hypocalcaemia

17
Q

What are the symptoms of hypercalcaemia?

A

“Stones, moans, (abdo) groans, and bones”

  • Renal stones
  • Depression, confusion, tiredness
  • Muscle weakness + GI pain inc. anorexia, PUD, pancreatitis
  • Bone pain and osteoporosis
  • Polydipsia and polyuria
  • Arrythmias, corneal calcification
18
Q

What investigations are done for hypercalcaemia?

A

Bloods:

  • ↑ Ca2+, ↓ (PO4)2-
  • ↑ ESR and hypercalcaemia => myeloma
  • PTH levels: ↑ in hyperparathyroidism, ↓ otherwise

DEXA bone scan

19
Q

How is primary hyperparathyroidism treated?

A

Surgical excision - of adenoma or all 4 glands in hyperplasia

20
Q

What are the causes of hypocalcaemia?

A

With high (P04)2- :

  • hypoparathyroidism
    [] primary = usually autoimmune
    [] pseudo = failure of receptor response to PTH, may be caused by hypomagnesaemia
    [] secondary = surgery/radiation of PT glands
  • vitamin D deficiency
  • Chronic renal failure
    [] due to ↓ vit D synth and ↑PO4 => ↓ GI absorption of Ca2+
    —————————————————————–

With normal/low (P04)2- :

  • Osteomalacia = decreased dietary intake, malabsorption
  • Pancreatitis
  • Alkalosis = total Ca2+ levels may be normal, but ionised will be reduced
21
Q

What are the symptoms of hypocalcaemia?

A 
Anxiety
Confusion
Nervous irritability/tetany
 - fasciculations and spasms
 - hyperreflexia
 - convulsions
Paraesthesia
ECG = prolonged ST segment and QT interval
22
Q

What are the symptoms of chronic hypocalcaemia?

A

Osteomalacia

Diarrhoea

23
Q

What are the signs of hypocalcaemia?

A

Chvostek’s sign - tapping the facial nerve cause brief ipsilateral facial spasm

Trousseau’s sign - arm spasm occurs after 1-4 mins of inflated BP cuff ~20mmHg

24
Q

What investigations should be done to diagnose hypocalcaemia?

A

Ca2+ an (PO4)2- levels
PTH levels
Parathyroid antibody levels

25
Q

How should hypocalcaemia be managed?

A

If acute/severe then:

  • calcium gluconate by IV infusion
  • check and correct hypomagnesaemia
  • check and correct alkalosis

If hypoparathyriodism/pseudohypoparathyroidism then:
- Vitamin D supplementation

Week 128 - Endocrinology (6 decks)

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