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ENDOCRINOLOGY > 8. Parathyroid & Parathyroid Hormone > Flashcards

8. Parathyroid & Parathyroid Hormone Flashcards

1
Q

Total body CALCIUM

A

approx 1kg

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2
Q

99% of body CALCIUM is stored where?

A

in BONES

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3
Q

what is CALCIUM in BONES stored as and what is its purpose

A

stored as HYDROXYAPATITE

for SKELETAL STRENGTH
& RESEVOIR FOR CALCIUM

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4
Q

remaining 1% of body CALCIUM is stored where… (3)

A

BLOOD, EXRRA-CELLULAR FLUID, SOFT TISSUES

Numerous important physiological functions:-
cell division, cell adhesion, glycogen metabolism, muscle contraction, neuronal excitability and coagulation

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5
Q

NORMAL SERUM of CALCIUM ranges between…

A

2.18 - 2.62 mmol/L

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6
Q

how are CALCIUM BLOOD LEVELS divided

A

45%- FREE or IONISED fraction and is BIOLOGICALLY FUNCTIONAL portion of total Ca.

45%- is BOUND to ALBUMIN in pH DEPENDENT manner.

10%- exists as a COMPLEX with ANIONS including
PHOSPHATE (PO4) and CITRATE.

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7
Q

PHYSIOLOGICAL FUNCTIONS of CALCIUM

A
  • CELL DIVISION
  • CELL ADHESION
  • PLASMA MEMBRANE INTEGRITY
  • PROTEIN SECRETION
  • MUSCLE CONTRACTION including CARDIAC muscle
  • NEURONAL EXCITABILITY
  • GLYCOGEN METABOLISM
  • BLOOD COAGULATION (clotting)
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8
Q

DAILY REQUIREMENTS of CALCIUM
INFANTS & CHILDREN:

A

350-550 mg/day

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9
Q

DAILY REQUIREMENTS of CALCIUM
TEENAGE GIRLS & BOYS:

A

800-1000 mg/day

(need most)

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10
Q

DAILY REQUIREMENTS of CALCIUM
ADULT MEN & WOMEN

A

700 mg/day

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11
Q

CALCIUM SOURCES:

A

milk, cheese and other dairy foods

green leafy vegetables – such as broccoli, cabbage and okra,
but not spinach

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12
Q

what play a major role in CALCIUM HOMEOSTASIS (3)

(Because of its physiological importance ECF concentration of Ca is
maintained within a narrow range.)

A

SKELETON
GUT
KIDNEYS

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13
Q

what is stimulated when BLOOD CALCIUM levels DROP - LOW CALCIUM

A

release of PTH (parathyroid hormone) from PARATHYROID GLAND

  • INCREASES BLOOD CALCIUM
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14
Q

effects of PTH on BONE to INCREASE CALCIUM

A
  • INHIBIT OSTEOBLASTS
  • STIMULATE OSTEOCLASTS

BREAKDOWN OF BONE, releasing calcium ions into bloodstream

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15
Q

effects of PTH on KIDNEYS to INCREASE CALCIUM

A

STIMULATES KIDNEY TUBULE CELLS to:
- RECOVER WASTE CALCIUM from the URINE
- RELEASE CALCITROL

  • CALCITROL STIMULATES INTESTINES to ABSORB CALCIUM from DIGESTING FOOD
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16
Q

what is the effect of CALCITROL on INTESTINES (released by kidney tubule cells, stimulated by PTH when calcium levels drop)

A

stimulate intestines to ABSORD CALCIUM from DIGESTING FOOD

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17
Q

upon effects of PTH (when calcium levels drop) BLOOD CALCIUM LEVELS INCREASE. what is secreted to regulate this

A

CALCITONIN from THYROID

act on BONE
- STIMULATE OSTEOBLASTS
- INHIBIT OSTEOCLASTS
CALCIUM REMOVED from BLOOD and used to BUILD BONE

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18
Q

80% of PHOSPHATE is STORED in… as…

A

stored in BONE as HYDROXYAPATITE

  • SKELETAL INTEGRITY
  • PRIMARY RESERVE
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19
Q

20% of PHOSPHATE is stored in…

A

SOFT TISSUES both in inorganic or organic molecules

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20
Q

PHYSIOLOGICAL FUNCTIONS of PHOSPHATE

A

Intracellular processes including
- NUCLEIC ACID SYNTHESIS
- ATP PRODUCTION (provides ENERGY at cellular level)
- KINASE and PHOSPHATASE ACTIVITY

21
Q

DAILY REQUIREMENT of PHOSPHATE / PHOSPHORUS

A

ADULTS - 550 mg/day

22
Q

PHOSPHATE SOURCES

A

Dairy
Red meat
Poultry
Bread

rice, oats

23
Q

PHOSPHATE BLOOD LEVEL RANGE

A

0.8-1.5 mmol/L

24
Q

systemic REGULATION of PHOSPHATE is maintained through…

A

PTH
VITAMIN D

INTESTINES
KIDNEY
BONES

25
Q

possible CAUSES of HYPOPHOSPHATAEMIA (low phosphate levels)

A
  • DECREASED INTESTINAL ABSORPTION (due to low dietary intake or condition affecting absorption)
  • INREASED RENAL WASTING (increased excretion, phosphate wasted)
  • REDISTRIBUTION FROM ECF INTO CELLS (common)
26
Q

clinical consequences of HYPOPHOSPHATAEMIA

A

poor growth in children
fatigue, weakness, loss of appetite
bone pain and fragile bones

  • 5% of hospitalised patients (30% in alcoholics)
27
Q

causes of HYPERPHOSPHATAEMIA (high phosphate levels)

A

DECREASED RENAL EXCRETION

ACUTE EXOGENOUS PHOSPHATE LOAD

REDISTRIBUTION of INTRACELLULAR PHOSPHATE to EXTRACELLULAR SPACE

28
Q

clinical consequences of HYPERPHOSPHATAEMIA

A

HYPOCALCAEMIA

SOFT TISSUE CALCIFICATION

CALCIFICATION of ARTERIES and HEART VALVES

29
Q

PARATHYROID GLANDS contain 2 main types of CELL:

A

CHEIF CELLS
OXYPHIL CELLS (no recognised physiological function)

30
Q

CHEIF CELLS of PARATHYROID GLANDS FUNCTION

A

FUNCTIONAL CELL

  • responsible for SYNTHESISING & SECRETING PARATHYROID HORMONES
31
Q

PARATHYROID GLANDS develop from ENDODERM of which PHARYNGEAL ARCHES

A

3 and 4

32
Q

PARATHYROID GLANDS are functional during GESTATION to..

A

control CALCIUM BALANCE in FETUS

33
Q

INITIAL state of PTH is as… with how many amino acids?

A

PRE-PRO-PTH
- 115 amino acids polypeptide

34
Q

PRE-PRO-PTH is CLEAVED to form… with how many amino acids?

A

PRO-PTH
- 90 amino acids polypeptide

35
Q

PRO-PTH is further CLEAVED to form…

A

active PTH
- 84 AMINO ACIDS

36
Q

how many amino acids in PTH

A

84

37
Q

CALCITRIOL is the end product of …. metabolism

A

VITAMIN D METABOLISM

38
Q

EFFECTS of PTH

A

INCREASE CALCIUM LEVELS

BONE:
stimulates osteoclasts to breakdown bone, Ca2+ released into bloodstream

KIDNEY:
reabsorption of calcium from urine
Calcitriol secretion by ACTIVATION OF VITAMIN D

Calcitriol acts on INTESTINES for reabsorption of calcium from foodb

39
Q

what is the effect of PTH on BONES that causes stimulation of Osteoclasts and Reabsorption of Bones to release Ca2+

A
  • STIMULATES OSTEOBLASTS
  • STIMULATES RANK LIGAND SYSTEM
  • allows for CHANGE from OSTEOBLASTS TO OSTEOCLASTS
40
Q

PTH action on KIDNEYS
besides increased Ca Reabsorption and Activation of Vitamin D

A

DECREASED PHOSPHATE REABSORPTION

41
Q

the effect of PTH on INTESTINES is due to

A

INCREASE IN ACTIVE VITAMIN D

  • increases absorption of CALCIUM and PHOSPHATE
42
Q

HYPERPARATHYROIDISM (HPTH):
PRIMARY (PHPT)

A

ABNORMALITY of the GLAND ITSELF

caused by Adenoma, Hyperplasia, rarely carcinoma

43
Q

HYPERPARATHYROIDISM (HPTH):
SECONDARY (SHPT)

A

compensatory OVER-SECRETION (too much PTH secreted when Ca low)

can be due to..
CKD - chronic kidney diseas
Vitamin deficiency (D)
malabsorption

44
Q

HYPERPARATHYROIDISM (HPTH):
TERTIARY (THPT)

A

after SECONDARY HYPERTHYROIDISM is TREATED

(still secreting high levels)

RARE

45
Q

Clinical features of HPTH - HYPERPARATHYROIDISM
usually due to HYPERCALCAEMIA

A

Nausea and vomiting
Constipation
ECG changes – short QT interval
Kidney stones
Bone pain
Osteoporosis
Psychosis
Altered mental status

46
Q

HYPOPARATHYROIDISM means

A

LOW PTH & LOW CALCIUM

47
Q

HYPOPARATHYROIDISM causes:

A
  • Surgical removal or damage
  • Auto-immune disorders
48
Q

what is PSEUDOHYPOPARATHYROIDISM

A

HIGH PTH

target organ RESISTANCE to PTH
(developmental disorder)

49
Q

CLINICAL FEATURS of HYPOPARATHYROIDISM and HYPOCALCAEMIA

A

Muscles:
WEAKNESS
MUSCLE CRAMPS

Nerve Function:
PERORAL (mouth) NUMBNESS, TINGLING
CHVOSTEK’S SIGN (twitch of facial muscles/spasm when tap)
TROUSSEAU’ SIGN (arm spasm with high pressure eg BP machine)
TENTAY (involuntary muscle contractions and overly stimulated peripheral nerves)

ENDOCRINOLOGY (11 decks)

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