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Pharmacology and Biochemistry > Clinical Chem 2nd lec > Flashcards

Clinical Chem 2nd lec Flashcards

1
Q

UNITS and VALUES

A

Calcium: 2.2 - 2.7 mmol/l (2.4 usually)

Phosphate: 0.85 - 1.45 mmol/l

Plasmaurate ≤ 0.6 mg/dL

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2
Q

Calcium

A

Present in 2 forms;

  • Bound to protein (albumin) -inactive
  • Free-ionised (Ca2+) -active

Bone as 99% reservoir, acts as buffer for calcium homeostasis

PTH, Calcitonin from thyroid, Vitamin D (1,25 dihydroxy-vitamin D, neccessary for PTH activity)

Hormonal control includes calcium and phosphate released from bone in response to PTH, PTH stimulates Ca2+ reabsorption and inhibits reabsoption of phosphate in renal tubular cells. Vitamin D promotes absorption of phosphate and calcium from GI tract.

Hypercalcaemia caused by inappropriate PTH secretion as in hyperparathyroidism (main cause)
- Usually d/t 1 or more parathyroid adenomas, hyperplasia of parathyroid glands or carcinoma of one of the glands

Clinical symptoms of hypercalcaemia - generalised ill health, renal calculi, bone pain

Primary hyperparathyroidism - increased plasmacalcium, decreased plasma phosphate, increased PTh

Hypercalcaemia not caused by inappropriate PTH - Vit D excess from over treatment of hypocalcaemia, sarcoidosis, or myeloma (calcitonin-like peptide)

Hypocalcaemia with hyperphosphataemia
- Primary hypoparathyroidism (low concentration of PTH), commonly caused by surgical damage to parathyroid glands)

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3
Q

1º Hypoparathyroidism

A
  • Decreased plasma calcium
  • Increased plasma phosphate
  • Decreased PTH
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4
Q

2º hyperparathyroidism (appropriate secretion of PTH)

A

Hypocalcaemia with hypophosphataemia

  • Osteomalacia (rickets in children), caused by long standing calcium, phosphate and vit D deficiency), predisposing factors include malnutrition, imparied absorption of vit D,impaired metabolism of vit D, renal tubular defects
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5
Q

Temporary hypocalcaemia

A

Due to post-operative hypoalbuminaemia (‘shock’)

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6
Q

Phosphate

A

85% in adults presents as calcium phosphate salts
- Remaining 15% ionised (H2PO4, HPO4-, PO42-) (Important intracellular anions that buffer H+ both in both fluids and urine)

Hormonal control - same hormones as calcium homeostasis which are PTH and Vit D

  • Both calcium and phosphate released from bone in response to PTH
  • PTH inhibits reabsorption of phosphate in renal tubular cells (stimulates Ca2+ reabsorption)
  • Vit D promotes absorption of phosphate and calcium from GI Tract
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7
Q

Hypophosphataemia

A
  • Disturbed calcium metabolism d/t high circulating PTH (affects renal tubular reabsorption of phosphate causing increase phosphate urinary excretion)
  • Hypophosphataemia also caused by severe and prolonged dietary deficiency
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8
Q

Hyperphosphataemia

A
  • Commonly caused by renal glomerular dysfunction

- Hypoparathyroidism

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9
Q

Plasma Calcium Levels UNTOUCHED, UNAFFECTED by

A
  • osteoporosis
    (Depletion of calcium from the body, slight increase in urinary calcium)
    Associated with low plasma oestrogen levels and endocrine disorders
  • Pagets disease
    (Disorganised osteoclastic + osteoblastic function)
    Increased freq. with age
    Bone pain
    PLasma Ca2+ and Phosphate rarely affected
    Plasma alkaline phosphatase typically very high
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10
Q

Calcium and bone disorders - TESTS (BIOCHEMICAL)

A
  • Plasma calcium + phosphate
  • Plasma Albumin + Urea
  • Plasma Alkaline + Phosphatase
  • Plasma PTH
  • Urinary Calcium + Phosphate
  • Plasma Vitamin D
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11
Q

Urate metabolism

A
  • End product of purine metabolism
  • Purines adenine + guanine are constituents of both types of nucleic acids
  • Purines used in the body derived from diet mainly meat or synthesized from small molecules
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12
Q

Hyperuricaemia

A
  • Men > women
  • Complication of alcoholism
  • After menopause > pre-menopause
  • Associated with hypercalcaemia
  • May be due to familial primary abnormality of purine metabolism or secondary to a variety of other conditions
  • May be asymptomatic or associated with gout
  • Contributing factors include increased rate of urate formation, reduced rate of excretion
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13
Q

Hyperuricaemia Dangers

A
  • Urate is poorly soluble in plasma
  • Ionisation of uric acid decreases as pH falls and therefore, less soluble
  • Crystalisation in joints causing gout
    Precipitation may occur in subcutaneous tissues (ears, olecranon, patellar bursae and tendons)
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14
Q

GOUT

A

Meds: ALLOPURINOL, ALLOXANTHINE, HYPOXANTHINE, XANTHINE

Symptoms: Stroke, heart failure, acute MI, renal damage by hypertension, hyperuricaemic nephropathy, urate stones, podagra (gout) Na+-urate crystals

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15
Q

Thyroid gland

A
  • Thyroxine (T4)
  • Tri-iodothyronine (T3)
  • Calcitonin

99% plasma T4 and T3 is protein bound to thyroxine-binding globulin (TBG)

1% free unbound fraction is the physiologically active form

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16
Q

Control of thyroid hormones

A

TSH stimulates synthesis and release of thyroid hormones from the thyroid gland
- Secretion of TSH from anterior pituitary gland is controlled by: circulating levels of thyroid hormones and thyrotrophin-releasing hormone

17
Q

Thyroid BIOCHEMICAL TEST

A
  • Plasma T4
  • Plasma TSH
  • Plasma T3
18
Q

Hyperthyroidism CAUSES

A
  1. Grave’s disease - autoimmune disease

2. Toxic nodules (single or multiple) - Plasma T4 and T3 raised, plasma TSH low

19
Q

Hypothyroidism CAUSES

A
  1. 1º hypothyroidism due to atrophic autoimmune thyroiditis, hashimoto’s disease, treatment of hyperthyroidism, drugs like carbimazole propylthiouracil, lithium carbonate
  2. 2º hypothyroidism
Plasma T4 
Plasma TSH (high in 1º, low in 2º)
20
Q

Reproductive hormones

A
  • Oestadiol
    [Mainly used to assist diagnosis of amenorrhoea, menopause, infertility, other endocrine conditions]
  • FSH
    [Stimulates development of ovarian follicles during the follicular stage of the menstrual cycle, in men stimulates testes to produce mature sperm]
    [Often used in conjunction w other tests; LH, testosterone, oestradiol, progesterone]

-LH
[High levels of LH and FSH mid-cycle cause ovulation]
[Stimulates ovaries to produce oestradiol]
[Stimulates Leydig cells in the testes to produce testosterone]

^ FSH and LH may cause developmental defects, polycystic ovary syndrome, ovarian tumour, adrenal disease, thyroid disease

In men
LH: controls production of testosterone from the testes
FSH: controls production of sperm

^^^ d/t primary testicular failure d/t developmental defects, testicular injury or pituitary or hypothalamic disorders

  • Progesterone
    [M/c to determine cause of inferitity or whether a woman has ovulated]
    [Peaks at day 21]
  • Testosterone
    [MEN Measured to investigate infertility and decreased sex drive/erectile dysfunction]
    [WOMEN measured to investigate infertility, amenorrhea, hirsutism, PCOS]

Pharmacology and Biochemistry (10 decks)

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