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HHD 2 > Calcium and Parathyroid > Flashcards

Calcium and Parathyroid Flashcards

1
Q

How many parathyroid glands are ususally present?

A

4
however this is variable

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2
Q

Where are parathyroid glands usually located?

A

posterior to the thyroid glands

can also be locate in the mediastinum?

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3
Q

Blood supply to the parathyroid glands mirror the thyroid glands. True or false

A

True

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4
Q

What pharyngeal pouch do the inferior parathyroid glands originate from?

A

pharyngeal pouch III

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5
Q

What pharyngeal pouch do the superior parathyroid glands originate from?

A

pharyngeal pouch IV

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6
Q

What are the main cell types in the parathyroid glands and their functions?

A
  • chief cells - produces PTH (parathyroid hormone)
  • Oxyphil cells- unknown function

Chief cells in stomach produce pepsinogen

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7
Q

What is the speculated function of the oxyphil cells?

A

may secrete excess PTH in cancer of the parathyroid gland

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8
Q

What is the main function of the parathyroid gland?

A

calcium homeostasis

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9
Q

Outline reasons why calcium homeostasis is important

A
  • coagulation- factors II, VII, IX, X are dependent on calcium as they are negatively charged
  • nerve depolarisation
  • skeletal/smooth/cardiac muscle contraction
  • enzyme co-factors
  • cardiac stability
  • bone and teeth
  • regulation of hormone secretion
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10
Q

Why is calcium important for cardiac stability ?

A
  • myocyte action potential/cardiac repolarisation cycle
  • phase 2 involves a calcium influx which slows down the rate of repolarisation (mediation of repolarisation)
  • also allows contraction of the the myocytes to carry on occuring
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11
Q

Calcium is the most abundant mineral in the body. True or false

A

True
body contains around 1kg of calcium

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12
Q

How is calcium homeostasis achieved?

A
  • bones
  • intestines
  • kidneys
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13
Q

Bones store 99% of the bodies calcium. How are bones involved in calcium homeostasis?

A
  • bone remodelling under control of PTH/calcitonin
  • osteoclasts resorb bone (release calcium into blood)
  • osteoblasts synthesise bone

osteoblasts send signals to osteoclasts before bone resorption occurs

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14
Q

When is parathyroid hormone released?

A

released when plasma/serum calcium levels are too low

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15
Q

When is calcitonin released?

A

released when plasma/serum calcium levels are too high
released from parafollicular cells

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16
Q

How are the intestines involved in calcium homeostasis?

A

they are involved in the absorption of calcium ions from the diet

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17
Q

How are the kidneys involved in calcium homeostasis?

A

majority of filtered calcium is reabsorbed in the kidneys
kidneys also convert inactive vitamin D into active vitamin D (calcitrol)

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18
Q

What is the function of parathyroid hormone?

A
  • increase serum calcium levels
  • stimulate osteoclast activity (bone resorbtion)
  • increases calcium reabsorption at the kidneys
  • increases phosphate excretion at the kidneys (less reabsorption of phosphate)
  • promotes kidneys to convert inactive vitamin D into calcitrol
19
Q

What is the function of calcitonin?

A
  • decreases serum levels of calcium
  • inhibits osteoclast activity- reduced bone resorption
  • increased calcium secretion at kidneys (less reabsorption)
  • decreases phosphate excretion at kidneys- increased phosphate retention; more phosphate moved into bones and bone fluid
20
Q

What is the function of calcitrol?

A
  • increased serum calcium levels
  • increased intestinal absorption of calcium
  • stimulates bone resorption (calcium mobilisation in bone)
  • increases calcium reabsorption at kidneys

similar action to PTH except PTH does not affect intestine

21
Q

What is the active form of vitamin D?

A

calcitrol
1,25 dihydroxyvitamin D

22
Q

How is the active form of vitamin D produced?

A
  • 7-dehydrocholesterol on the skin converted into cholecalciferol (vitamin D3)
  • Vitamin D3 (fish, meat), vitamin D2 (supplements) are obtained via dietary intake
  • vitamin D3 (cholecalciferol)/D2 are then 25 hydroxylated in the liver to produce 25-hydroxycalciferol
  • additional hydroxylation then takes place in the kidney to produce 1,25 hydroxycholecalciferol
23
Q

Vitamin D deficiency causes ________ in children

A

rickets
soft bone which spreads under pressure
pelvic, femural, tibial abnormalities

24
Q

What is the main function of vitamin D (aside from its role in calcium homeostasis)?

A

augment immune function

25
Q

What are the symptoms of a vitamin D deficiency?

A
  • excessive sweating
  • high blood pressure
  • tiredness and fatigue
  • digestive problems
  • mood swings
  • impaire immunity
  • psoriasis
  • overweight/obese
  • pain
26
Q

What patients are at risk of vitamin D deficiency?

A
  • infants and children aged under 4
  • pregnant and breastfeeding women, particularly teenages and young women
  • people over 65
  • people who have low or no exposure to the sun e.g. those who cover the skin for cultural reasons, who are housebound or confined indoors for long periods
  • people with darker skin, for example people of african, afro-carribean or south asian family origin
27
Q

What is hypercalcaemia?

A

this is when serum calcium levels >2.6mmol/L

28
Q

What are the causes of hypercalcaemia?

A

primary hyperparathyroidism- overproduction of PTH (adenoma, adenocarcinoma, hyperplasia)
cancer >90% of cases

29
Q

What is the classic presentation of hypercalcaemia?

A

Stones
Bones
Groans
Psychiatric moans

  • renal stones (calcium oxalate); submandibular stones, lower prevalence in parotid
  • bone pain due to osteoporosis
  • abdominal pain, constipation and myalgia- pancreatitis, stomach ulcers
  • poor sleep, fatigue, depression, psychosis

Polydipsia and polyuria also observed in hypercalcaemia in a similar way to glycosuria; calcium and glucose drag water out when not reabsorbed; leads to dehydration of cells hence polydipsia and resulting polyuria

30
Q

What is the cause of primary hyperparathyroidism?

A
  • overproduction of PTH by parathyroid
  • male >female
  • > 80% of cases due to a single adenoma
  • elevated calcium with normal or elevated PTH
31
Q

What is the cause of secondary hyperparathyroidism?

A
  • excessive PTH production in response to chronically low Ca2+ ions; usually as a result of chronic renal failure - kidney failing to reabsorb calcium ions
  • decreased calcium levels with elevated PTH
32
Q

What is the cause of tertiary hyperparathyroidism?

A
  • parathyroid gland is chronically overstimulated, continues to produce excessive PTH despite normalisation of calcium
  • elevated calcium and elevated PTH
    *[resolution of kidney problems by parathyroid gland now programmed to overproduce PTH]
33
Q

What investigations can be carried out for a diagnosis of hyperparathyroidism ?

A
  • serum calcium, PTH and vitamin D
  • DEXA scan- bone density scan for osteoporosis
  • CT neck for surgical plannin- adenomas/lumps
34
Q

How can primary hyperparathyroidism be managed?

A
  • parathyroidectomy (adenoma)
  • monitor calcium levels annually
  • avoid medication that increases calcium levels (thiazide diuretics, lithium)
  • +/- vitamin D supplementation
  • +/- bisphosphonates
35
Q

What is hypocalcaemia ?

A

serum calcium levels of <2.1mmol/L

36
Q

What are the causes of hypocalcaemia?

A

most commonly hypoparathyroidism (autoimmne or iatrogenic)
* vitamin D deficiency
* alcoholism
* eating disorders
* CRF- chronic renal failure- failure to reabsorb
* osteoporosis treatment
* vomiting

37
Q

What are the clinical signs of hypocalcaemia?

A

[CATS go numb]

  • convulsions
  • arrhythmias (prolonged QT interval on ECG)
  • Tetany, chvosteks sign, trousseaus sign
  • parasthesia in hands, feet and mouth (go numb)
38
Q

What is Chvostek sign?

A

facial nerve spasm/twicth
tap cheek; a twitch of facial muscle is observed

39
Q

Tetany Vs tetanus

A

Tetanus is an infection
Tetany- hypocalcaemic hyper-reactive nerves

40
Q

What investigations are required for hypoparathyroidism?

A
  • ECG
  • vitamin D
  • thyroid function
  • renal ultrasound
41
Q

80% of hypoparathyroidism have a ___________ cause.

A

post-surgical

42
Q

What is the management of hypoparathyroidism?

A
  • severe: IV calcium with ECG monitoring
  • mild/moderate: oral Ca2+, PTH, thiazide diuretic
43
Q

What are the dental considerations for hyperparathyroidism?

A
  • osteoporosis
  • in children- tooth development defect and alteration in dental eruption
  • in adults- drifting of teeth, complaint of jaw pain, sensitive teeth when chewing and soft tissue calcifications
  • malocclusion due to drifting teeth, spacing of teeth may be the first signs of the disease
  • prone to developing cystic lesions around the mandible
  • brown tumours- filled with giant osteoclastic cells driven to increase calcium levels; granulomatous tissue
  • no lamina dura lining the socket; due to mobilisation of calcium from bone
44
Q

What are the dental considerations for hypoparathyroidism

A
  • enamel hypoplasia-not enough crown
  • delayed eruption
  • poorly calcified dentin
  • pulp calcifications
  • malformed roots
  • parasthesia in mouth [CATs go NUMB]
  • Facial muscle abnormalities- hyperactive nerves- due to hypocalcaemia

HHD 2 (37 decks)

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