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Endocrinology > Parathyroid Disease + Ca Metabolism > Flashcards

Parathyroid Disease + Ca Metabolism Flashcards

1
Q

What are the 4 main calcium regulatory hormones?

A
  • PTH
  • Mg
  • Vitamin D (active form - calcitriol)
  • Caclitonin
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2
Q

When is PTH released normally and what does it require?

A
  • Released in response to low Ca serum levels
  • Requires Mg. Low levels of Mg cause a drop in PTH hence causing hypocalcaemia and hypokalaemia
  • Hypokalemia as Mg is required for Na/K ATPase pump to function
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3
Q

What are the causes of hypomagnesia?

A
  • Malabsorption through PPI use
  • Loop Diuretics
  • Chronic Alcoholism with alcohol withdrawal
  • Cirrhosis
  • Renal tubular disorders
  • Chronic mineralocorticoid excess
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4
Q

What are the 3 main ways PTH increases serum Ca levels?

A
  • Increased osteoclast activity
  • Increase in Ca reabsorption in the kidney
  • Activation of 1, 25 - dihydroxy - vitamin D production, increasing Ca absorption in the gut
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5
Q

What are the 2 steps in vitamin D production?

A
  1. In the liver, converted to 25 - dehydroxy - vitamin D

2. In the kidney, this is converted to the active form calcitriol

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6
Q

What are the actions of vitamin D?

A
  • Increase in Ca absorption in the gut
  • Increase in PTH release
  • Enhances bone turnover
  • Increases Ca and phosphate reabsorption in the kidney
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7
Q

How is adjusted calcium calculated?

A

=> Allows for the changes in albumin concentration

Ca x 0.02 x (40 - [albumin])

Eg. Albumin = 50

Ca - (0.02 x 10)

Eg. Albumin = 20

Ca + (0.02 x 20)

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8
Q

What are the causes of hypercalcaemia?

A

=> Most common:

  • Primary hyperparathyroidism
  • Multiple Myeloma (Malignancy)
  • Sarcoidosis

=> Less common causes:

  • Familial Hypocalciuric Hypercalcaemia
  • Thyrotoxicosis
  • Thiazides
  • Renal transplant

=> Rare:

  • Lithium
  • TB
  • Long term hospital admission
  • Vitamin D therapy
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9
Q

What are the three different types pf Hyperparathyroidism?

A

=> Primary hyperparathyroidism:

  • Parathyroid adenoma or hyperplasia of gland
  • Can result in osteopenia if too much bone resorption
  • Treatment involves surgery to remove the adenoma in cases of following:
  • Serum calcium 1 mg/dL above normal
  • Age > 50
  • Hypercacliuria > 400 mg/day
  • Creatinine clearance < 30% of normal
  • Episodes of life threatening hypercalcaemia
  • Nephrolithiasis
  • Neuromuscular symptoms
  • Reduction in bone mineral density

=> Secondary hyperparathyroidism:

  • Although PTH high, Ca is low due to kidney issues
  • Low Ca in turn causes compensatory hyperplasia of parathyroid gland, which is why PTH levels are high
  • Usually managed medically but can be surgically removed in causes of bone pain, persistent pruritus or soft tissue calcifications

=> Tertiary hyperparathyroidism:

  • Hypertrophy of parathyroid gland due to long standing secondary hyperparathyroidism
  • Treated through removal of parathyroid gland
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10
Q

What are the two main causes of hypercalcaemia due to malignancy?

A
  • Secretion of PTHrp - PTH related peptide (squamous cell carcinoma)
  • Direct invasion of bone that increases bone metabolism
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11
Q

What are the clinical features of hypercalcaemia?

A

=> Bones, stones, groans and psychic moans

  • General malaise
  • Bone pain
  • Nausea
  • Depression
  • Abdo pain
  • Constipation
  • Raised BP

Shortened QT interval

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12
Q

What are the investigations in suspected hypercalcaemia?

A

=> Bloods
Low Albumin indicates malignancy
High PTH indicates hyperparathyroidism

=> Serum electrolytes
Low Cl, low K, high PO4 indicates malignancy

=> 24 hour urinary calcium
Excludes familial hypocalciuric hypercalcaemia

=> CXR
Bone status

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13
Q

What is the management of hypercalcaemia?

A
  • Correct dehydration, give SALINE
  • Give BISPHOSPHONATES, which inhibit osteoclast activity hence decreasing bone resorption
  • Further management with chemotherapy in cases of malignancy
  • CALCITONIN works faster than BISPHOSPHONATES
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14
Q

What are the causes of hypocalcaemia?

A
  • Hypoparathyroidism

=> Pseudohypoparathyroidism:

  • Target cells become insensitive to PTH
  • Associated with low IQ, low stature, and shortened 4th and 5th metacarpals
  • Low Ca, high phosphate and high PTH
  • Diagnosis made through measuring cAMP and phosphate levels following PTH infusion
  • In normal hypoparathyroidism, infusion increases their levels, but in this case there is no increase
  • Hypomagnesia (less Mg so PTH does not work)
  • Hungry bone syndrome
  • Neonatal hypocalcaemia
  • Acute Pancreatitis
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15
Q

What are the main causes of vitamin D deficiency?

A
  • Malabsorption
  • Reduced sun exposure
  • Anti-epileptic drugs
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16
Q

What are the clinical features of of hypocalcaemia?

A

Use MNEUMONIC SPASMODIC

S - Spasms (Tetany)
P - Perioral paraesthesiae (numb tingling feeling)
A - Anxious, irritable, irrational
S - Seizures
M - Muscle tone
O - Orientation impaired
D - Dermatitis
I - Impetigo Herpetiformis
C - Chvostek's sign (tapping of facial nerve causing twitching)

You also see Trosseau sign - inflating BP cuff above systolic pressure and waiting 3 minutes. Hand goes into Tetanic spasm

Prolonged QT interval

17
Q

What are the investigations in suspected hypocalcaemia?

A

Check PTH Levels

=> LOW:
- Hypoparathyroidism

=> HIGH:
- Check Vitamin D levels

=> VITAMID D LEVELS HIGH:
- Pseudohypoparathyoidism

=> VITAMIN D LEVELS LOW:
- Vitamin D deficiency

18
Q

What is the management of hypocalcaemia?

A

MILD => Give Ca 5 mmol/6hrs
SEVERE => IV Calcium glutonate 10mL at 10%
In CKD => ALFACALCIDOL (active metabolite of vitamin D)

=> Monitor ECG for prolonged QT

19
Q

What are the complications of hypocalcaemia?

A
  • Osteomalacia/Rickets

- Osteoperosis

20
Q

What is the difference between osteomalacia and osteoperosis?

A
  • Osteomalacia is a decrease in the mineral content of the bone
  • Osteoperosis is a reduction in bone mass
21
Q

What are the causes of osteomalacia?

A
  • Vitamin D deficiency
  • Drug induced
  • Liver disease
22
Q

What is the mian manifestation of Vitamin D deficiency?

A
  • Rickets in children causes growth retardation and hyotonia

- Osteomalacia is adults

23
Q

What are the investigations in suspected osteomalacia?

A

=>Serum 1,25-dihydroxy-vitamin D
Low

=> CXR
- Shows defective mineralisation

24
Q

What are the risk factors of osteoperosis?

A
  • Steroids
  • Hyperthyroidism
  • Alcohol
  • Early menopause
  • Low Ca
25
Q

What are the clinical features of osteoperosis?

A
  • Bone fractures involving thoracic/lumbar vertebrae, proximal femur and distal radius
26
Q

What are the investigations in suspected osteoperosis?

A

=> DEXA scan:
Gives a T score
-1 to -2.5 - OSTEOPENIA
-2.5 or lower - OSTEOPEROSIS

27
Q

What is the management of osteoperosis?

A
  • Conservative or medical management
  • Conservative management involves changes in lifestyle
  • Medical management involves use of:
    BISPHOSPHONATES
    HRT
    CALCITONIN
28
Q

What is Familial Hypocacliuric Hypercalecemia?

A
  • Autosomal dominant condition

- Defect of calcium sensing receptor

Endocrinology (8 decks)

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