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Medicine > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

GFR depends on

A

Number of functioning nephrons
Glomerular function
Intracapillary function
Tubular luminal pressure

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2
Q

AKI stages and causes

A

Rise in creatine or fall in urine output over hours to days
Stage 1: 1.5-2.0 x increase or 26mcmol/L and more increase in 48h
Stage 2: 2.0-3.0 x increase
Stage 3: >3 x increase or 1.5 x to 354 mcmol/L
Causes: hypovolaemia, pump failure, ischaemia, nephrotoxis, glomerulonephritis, interstitial nelhritis, stones , tumour, prostate

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3
Q

AKI risks

A 
75 +
Hypertension
CKD
DM
Chronic liver disease
CCF
Myeloma
Sepsis
Drugs
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4
Q

Vasopressin

A

Hypothalamus (supra-optic and paraventricular nuclei)
Goes to kidney > increases water permeability > increased water reabsorption > decreased plasma osmolality
Stimuli for vasopressin release:
Increased plasma osmolality, drugs, stress, decreased blood volume

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5
Q

eGFR

A

Creatinine production rate depends on:

Muscle mass: age and sex (co-efficients for female and africans)

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6
Q

CKD causes

A 
DM
Hypertension
Polycystic kidney disease
Glomerulonephritis, pyelonephritis, interstitial nephritis
Multi-system disease
Drugs
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7
Q

CKD consequences

A

Stage 3a: hypertension/CVD risk
Stage 3b: low calcium, 2o increased PTH
Stage 4: +anaemia, anorexia, high phosphate
Stage 5: +salt and water retention,acidosis and increased K

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8
Q

CKD - biochemistry changes

A 
Increased urea and creatinine
Increased phosphate 
Decreased 1alfa OH-vit D > reduced gut Ca absorption > 2o hyperparathyroidism
Hyperkalaemia
Reduced EPO
High cholesterol
High triglycerides
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9
Q

Anterior Pituitary production

A 
TSH
ACTH
FSH and LH
Growth hormone
Prolactin
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10
Q

Anterior pituitary investigations

A 
Basal hormone measurements:
Pituitary hormones
Target hormones
Stimulation testing:
ACTH - hypoglycaemia, CRF
TSH - TRH
LH/FSH - LHRH
GH - Hypoglycaemia
Suppressing test
Suppression test
ACTH - dexamethasone
GH - glucose
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11
Q

GH excess symptoms and signs

A 
Acroparaesthesia
Amenorrhoea
Reduced libido
Headache
Increased sweating
Snoring
Arthralgia - carpal tunnel
Backache
Pituitary gigantism
Impaired glucose tolerance
Vascular: increased BP, cardiomegaly, arrhythmias
Increased colon cancer risk
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12
Q

GH excess investigations

A

Basal GH and IGF1

GTT - suppression test

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13
Q

GH deficiency

A

Children - short stature
Adults - significance less clear
Causes:
Destructive - tumours, surgery, irradiation, meningitis, head injury
Functional - psychosocial, endocrine abnormalities, laron dwarfism (GH R defect)
Dx: Basal, stimulation (insulin, glucagon, arginine maybe GHRH, clonidine), failure of two stimuli required

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14
Q

Thyroid hormones

A 
T3 ~5x as active as T4
T4 secreted solely from thyroid
T3 <20% secreted from thyroid, majority peripheral de-ionisation of T4
3 proteins bind thyroid hormone:
Thyroid binding globulin (TBG)
Thyroid binding pre-albumin
Albumin
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15
Q

Primary hypothyroidism

A

Biochemical features: raised TSH, low FT4, FT3 (not helpful)
Clinical features: lethargy, tiredness, weight gain, cold intolerance, coarsening of hair and skin, slow reflexes, hoarseness, constipation, menstrual abnormalities, bradycardia

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16
Q

Compensated hypothyroidism

A

Biochemical features: raised TSH (4-15), low normal FT4, +ve anti-thyroid peroxidase antibodies

17
Q

Primary hyperthyroidism

A

Biochemical features: undetectable TSH, raised FT4, raised FT3
Clinical features: weight loss, heat intolerance, palpitations, agitation, tremor, muscle weakness, diarrhoea, thyroid eye disease, menstrual abnormalities.

18
Q

Cortisol

A

Production rate 25mg/d
90% protein bound (CBG+Albumin)
Effects:
Carbohydrate metabolism (insulin antagonist, gluconeogenesis)
Protein catablosim
Immunosuppression
Permissive action (catecholamines, free water clearance)

19
Q

Adrenal insufficiency consequences

A 
Hypoglycaemia
Hyponatraemia
Hyperkalaemia
Hypotension
Pigmentation
Non-specific
20
Q

Renal insufficiency investigations

A 
Serum cortisol limited value although >350 at 8-9am diagnosis unlikely
Dynamic synacthen stimulation test
Short: 250mcg given IM
Normals: absolute rise >420nmol/L
ACTH differanties 1o/2o
21
Q

21-hydroxylase deficiency (CAH)

A

> 90% of CAH
Marker - increased 17alpha OH progesterone
Classical form:
Simple virilising (ambiguous external genetalia, pigmanted scrotum)
Salt wasting
Sudden unexplained deaths in newborn males
Late-onset form:
Hirtuism
Menstrual cycle disorder
Subfertility

22
Q

Hypercortisolism (Cushing’s)

A 
ACTH high:
Pituitary tumour (cushing’s disease)
Ectopic tumour
ACTH low:
Adrenal adenoma/carcinoma
Iatrogenic
Pseudo-cushing’s: alcohol abuse, obesity, depression
23
Q

Cushing’s clinical features

A 
Mental disturbances
Fat redistribution (truncal obesity)
Striae
Hyperandrogenism
Hirtuism
Acne
Amorrhoea
Protein catabolism
Osteoporosis
Poor wound healing
Bruising
Insulin resistance
Glucose intolerance
Salt retention
Hypertension
Immunosuplression
24
Q

Yanovski test

A

Dexamethasone supressed CRH test

Differentiates patient’s with cushing’s syndrome, and those with pseudo-cushing states

25
Q

Anterior pituitary - ovarian axis

A

GnRH secreted from hypothalamus
Cause release of LH and FSH
FSH acts on follicular granulosa cells
LH acts on theca and mature granulosa cells

26
Q

Assessment of ovulation

A 
Progesterone:
>30 ovulation
<30 reduced conception rate
If low level repeat next cycle
Timing:
Day 21 progesterone
7 days before menses
27
Q

Primary ovarian failure

A

Impaired follicular development
High LH/FSH (esp. FSH)
Low oestradiol

28
Q

Causes of ovarian failure

A 
Premature ovarian failure
Post menopausal
Autoimmune damage
Surgery
Irradiation
Dysgenesis (turner’s)
29
Q

Primary ovarian failure diagnosis

A

FSH is the single most useful test
Not recommended in healthy women >45 w/ symptoms
Appropriate in women between 40-45 w/ symptoms
Women < 40 confirm raised FSH in 2 samples 6wks apart

30
Q

Secondary ovarian failure

A

Impaired LH/FSH production
Low LH/FSH
Impaired follicular development
Low oestradiol

31
Q

Cause of secondary ovarian failure

A

LHRH deficiency
Pituitary tumours (pro-lactinoma)
Secondary hypopituitarism (irradiation, infiltrative and vascular disorders)
Functional: weight loss, stress, exercise, starvation
Systemic disease: thyroid, adrenal

Medicine (4 decks)

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