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parathyroid glands Flashcards

1
Q

what are the parathyroid glands composed of

A

chief cells

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2
Q

what do the parathyroid gland chief cells secrete

A

PTH

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3
Q

what does PTH act on

A

CASR (calcium sensing receptor)

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4
Q

what kind of receptor is the CASR

A

GPCR that regulates extracellular calcium homeostasis

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5
Q

what do chief cells look like

A

round cells with moderate cytoplasm and bland round central nuclei

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6
Q

what cells support the chief cells

A

oxyphil cells (slightly larger with acidophilic cytoplasm)

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7
Q

what does PTH do to osteoclast activity

A

increases osteoclast activity releasing Ca and phosphate

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8
Q

what does PTH do to small bowel absorption of calcium and phosphate

A

indirectly increases small bowel absorption of Ca and phosphate by activating vitamin D

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9
Q

what does PTH do to kidney reabsorption of calcium

A

increased calcium reabsorption in distal tubule

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10
Q

what does PTH do to phosphate excretion in kidney

A

decreased phosphate excretion in proximal tubule

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11
Q

what effect does increased serum calcium have on PTH secretion

A

negative feedback

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12
Q

what are the 4 main symptoms of hypercalcaemia

A

BONES
MOANS
STONES
GROANS

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13
Q

BONES

A

pain
fracture
osteoporosis
osteitis fibrosa cystica

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14
Q

what is osteitis fibrosa cystica

A

resorption of bone leading to fibrosis and cystic spaces

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15
Q

what ix should be done in ‘bones’ symptoms of hypercalcaemia

A

DEXA

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16
Q

STONES

A

nephrolithiasis and complications

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17
Q

GROANS

A

GI complications - nausea, constipation, peptic and duodenal ulcers, acute pancreatitis, gall stones, abdominal pain

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18
Q

MOANS

A

depression, lethargy, seizures, weakness and fatigue

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19
Q

what are some other symptoms of hypercalcaemia

A

nephrocalcinosis - calcification of renal tubules - can lead to renal insufficiency and polyuria
calcification of the aortic and mitral valves
hypertension

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20
Q

what are s/s of acute hypercalcaemia

A

thirst
dehydration
confusion
polyuria

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21
Q

what is the treatment of acute hypercalcaemia

A 
fluids (0.9% saline, 4-6L in 2 hours)
loop diuretics (avoid thiazide)
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22
Q

what is the treatment of acute hypocalcaemia

A

IV calcium gluconate (10ml in 50ml saline or dextrose)

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23
Q

what are some s/s of hypocalcaemia

A 
muscle weakness
muscle spasm (tetany)
muscle cramps
fits
fatigue
paraesthesia of fingers, toes and perioral area
bronchospasm or laryngospasm
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24
Q

what is an ECG change of hypocalcaemia

A

QT prolongation

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25
what 2 signs are positive in hypocalcaemia that show muscle spasm/tetany
Chovslek's sign - tapping over facial nerve | Trosseau sign - carpopedal spasm - filling of a BP cuff
26
how is vitamin D3 formed
by the skin on exposure to the sun
27
where can you get Vitamin D3 and D2
from diet
28
the liver metabolises vitamin D3 to
25-OH-vitamin D
29
the kidney metabolises 25-OH-vitamin D to
1,25-hydroxy vitamin D
30
in what condition will almost always develop a parathyroid adenoma and hypercalcaemia at a young age
MEN 1/2
31
what are some causes of hypocalcaemia
``` hypoparathyroidism vit D deficiency chronic renal failure pancreatitis hyperventilation osteoblastic bone mets rhabdomyolysis high turnover - bed ridden, thyrotoxic, Pagets granulomatous disease e.g. sarcoid/TB drugs - Vit D, thiazides, lithium ```
32
``` primary hyperparathyroidism biochemistry: Ca PTH Phosphate urinary cAMP ALP ```
``` HIGH Ca HIGH PTH low phosphate HIGH urinary cAMP HIGH ALP ```
33
what is primary hyperparathyroidism
primary overactivity of the parathyroid galnds
34
what are the 4 main causes of primary hyperparathyroidism
adenoma hyperplasia carcinoma malignancy
35
what is the most common cause of primary hyperparathyroidism
adenoma
36
how many glands are affected in parathyroid adenoma
just one - other glands are atrophic
37
how does an parathyroid adenoma usually present
usually asymptomatic hypercalcaemia but may get BSMG
38
what is the treatment of a parathyroid adenoma
removal of affected gland
39
although an adenoma may resemble a normal parathyroid gland microscopically, what might you see
fibrous connective tissue capsule with adjacent rim of compressed parathyroid tissue
40
what syndromes is parathyroid hyperplasia associated with
MEN 1 / MEN2b
41
parathyroid hyperplasia usually involves what glands
all glands
42
what is the treatment of parathyroid hyperplasia
removal of all affected glands
43
what % of primary hyperparathyroidism is due to hyperplasia
5-10%
44
what % of primary hyperparathyroidism is due to carcinoma
1%
45
what are some complications of parathyroid excision
recurrent laryngeal nerve palsy hypoparathyroidism low Ca - hungry bone sydrome
46
what cancer causes a paraneoplastic syndrome there there is release of PTHrp from solid tumours
squamous cell lung cancer | breast/renal cell carcinomas
47
how is hyperparathyroidism caused by malignancy diagnosed
``` raised Ca and ALP xray CT MRI isotope bone scan ```
48
what is PTH like in hyperparathyroidism caused by malignancy
PTH low - PTHrp causes high Ca which negatively feeds back to PTH
49
what is familial isolated hyperparathyroidism
inherited form of hyperparathyroidism | get an adenoma
50
what are the indications for a parathyroidectomy
end organ damage (bone disease, gastric ulcers, renal stones) Ca > 2.85 < 50 eGFR < 60
51
what is secondary hyperparathyroidism
chronic hypocalcaemia causes compensatory over activity of the parathyroid glands
52
``` secondary hyperparathyroidism biochemistry Ca PTH phosphate ALP ```
LOW calcium HIGH PTH HIGH phosphate raised ALP
53
what is the most common cause of secondary hyperparathyroidism
chronic renal failure
54
how does chronic renal failure lead to secondary hyperparathyroidism
renal insufficiency leads to decreased phosphate excretion increased serum phosphate binds to free Ca decreased free Ca stimulates all 4 parathyroid glands increased PTH ---> bone resorption
55
what is the parathyroid tissue like in secondary hyperparathyroidism
hyperplastic
56
what is the treatment for secondary hyperparathyroidism
phosphate binders | vit D
57
what else might be raised in secondary hyperparathyroidism
25-OH vit D | metabolised by the kidneys so accumulation
58
what is tertiary hyperparathyroidism
parathyroid gland becomes autonomous due to many years over over activity e.g. in renal failure
59
tertiary hyperparathyroidism biochemistry Ca PTH Phosphate
HIGH Ca HIGH PTH raised phosphate
60
what is cinacalcet
calcium mimetic
61
when is cinacalcet used
tertiary hyperparathyroidism carcinoma primary if not fit for surgery
62
how does cinacalcet decrease PTH
increases sensitivity of parathyroid cells to Ca so decreases PTH secretion
63
familial hypocalciuric hypercalcaemia biochemistry Ca urine Ca PTH
mild hypercalcaemia decreased urine calcium excretion marginally elevated PTH usually benign/asymptomatic
64
what is the inheritance of FHH
autosomal dominant
65
what is the genetic cause of FHH
deactivating mutation in CASR
66
what does vit D deficiency lead to with regard to calcium levels
low calcium
67
``` Low calcium muscle wasting - proximal myopathy dental defects (Caries, enamel) tender bones/fractures/rib deformitity/limb deformity waddling gait loosers zones ```
osteomalacia | rickets in children
68
what is Vitamin D resistant rickets
X linked hypophosphataemia
69
what is the gene mutation in X linked hypophosphataemia
PHEX or FGF23
70
what does the FGF23 gene usually do
regulates phosphate levels in plasma
71
what are the levels of phosphate and vitamin D like in vitamin D resistant rickets
high vitamin D | low phosphate
72
what is the treatment for vitamin D resistant rickets
phosphate and vitamin D supplements
73
what are some long term consequences of vitamin D deficiency
bone disease malignancy (esp colon) heart disease diabetes
74
what is the treatment for vitamin D deficiency
Vit D3 tablets calcitrol alfacalcidol combined calcium + vit D e.g. adcal D3
75
what is the PTH and Ca level in hypoparathyroidism
low PTH | low Ca
76
what is the treatment of hypoparathyroidism
calcium supplements and vitamin D tablets calcitrol synthetic PTH
77
is hypo or hyper parathyroidism more common
hyper | hypo is very rare
78
what are some causes of hypoparathyroidism
``` usually post op - surgery/radiotherapy malignancy congenital absence - Di George Syndrome (22q11.2) familial hypomagnesaemia ```
79
how does hypomagnesaemia cause hypoparathyroidism
calcium release from cells + PTH secretion both rely on magnesium
80
what is the treatment of hypomagnesaemia
calcium and magnesium replacement
81
what can cause hypomagnesaemia
alcohol, drugs (thiazide, PPI), GI illness, pancreatitis, malabsorption
82
what is pseudohypoparathyroidism
failure of target cell response to PTH
83
what is the genetic defect in pseudohypoparathyroidism
dysfunction of G protein (Gs alpha subunit) | GNAS-1 gene
84
what is the biochemistry of pseudohypoparathyroidism Ca phosphate PTH
Low Ca High phosphate High PTH
85
what are some s/s of pseudohypoparathyroidism
``` obesity/round face subcutaneous calcification learning disability calcified basal ganglia AD form assoc. short stature and brachydactylyl of 4th and 5th metacarpals bone abnormalities ```
86
what is the treatment of pseudohypoparathyroidism
calcium and vit D supplements
87
what is pseudopseudohypoparathyroidism
normal biochemistry but morphological features of pseudohypoparathyroidism
88
what is another name for pseudopseudohypoparathyroidism
albright's hereditary osteodystrophy
89
what is a sign of mccune albright syndrome in bones
areas of abnormal fibrous scarring in bones

year 2 (19 decks)

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