Case 10 Flashcards
Effect of Thyrotropin releasing hormone (TRH)
Thyroid stimulating hormone release from anterior pituitary
Proportion of anterior pituitary which secretes TSH
3-5%
Effect of GHRH
GH release from anterior pituitary
Effect of GnRH
Gonadotrophin release from anterior pituitary (LH and FSH)
Effect of corticotropin releasing hormone
ACTH release from anterior pituitary
GH deficiency in children
Short stature
GH deficiency in adults
Reduced muscle mass and performance
LH deficiency in men
Hypogonadism, reduced sperm count
LH deficiency in women
Hypogonadism, amenorrhoea
FSH deficiency
Infertile
TSH deficiency
Hypothyroidism
ACTH deficiency
Loss of pigmentation
Hypoadrenalism
Prolactin deficiency
Rare
Sheehan’s Syndrome - failure of lactation
Effects of TSH
Synthesis of Thyroglobulin (Tg)
Iodide ion uptake from blood into thyroid cells
Iodination of tyrosine residues on Tg - producing T4 and T3
T4
Thyroxine
T3
3,5,3’-Triiodothyronine
Predominantly circulating thyroid hormone
T4
Biologically active thyroid hormone
T3
Target for ACTH
Adrenal Gland
Adipocytes
Melanocytes
Target for GH
All tissues
Particularly liver
Target for FSH and LH
Gonads
Target for TSH
Thyroid gland
Zona glomerulosa
Release of Aldosterone
Outermost layer of adrenal cortex
Zona fasciculata
Release of cortisol
Middle layer of adrenal cortex
Zona reticularis
Release of DHEA
Innermost layer of adrenal cortex
Sella Turcica
Bone within which the hypothalamus sits
“Turkish cellar”
Symptoms of upward extending enlarged pituitary
Headache
Loss of visual acuity
Bitemporal hemianopia
(Compression of optic chiasm)
Enlarged pituitary causes
Headache
Causes of Hypothyroidism
Autoimmune - Hashimoto Thyroiditis
Ablative therapy (destruction of thyroid tissue)
Iodine deficiency
Idiopathic
Symptoms of Hypothyroidism
Fatigue Weight gain Cold intolerance Constipation Menstrual irregularity Joint pain and muscle cramps Infertility
Signs of Hypothyroidism
Hypothermia Periorbital puffiness Oedema Hypothermia Rough, dry skin Bradycardia Peripheral neuropathy (delayed relaxation of ankle jerk) Loss of outer 1/3 of eyebrow Hoarseness
Function of thyroid hormones
Increase BMR
Long bone growth and Neural maturation
Increase sensitivity of body to catecholamines
Myxoedema Coma
End stage hypothyroidism (if poorly controlled)
Elderly, obese female becoming increasingly withdrawn /sleepy/confused.
Slips into a coma
Lab results for primary hypothyroidism
Low T4
High TSH
Hyponatraemia
Raised LFTs (Bilirubin, lactate dehydrogenase, creatinine kinase, ALT)
Euthyroid Sick Syndrome
Low T3
Normal T4
Normal or low TSH
Cause of hyperthyroidism with low TSH
Graves Disease (Autoimmune, thyroid stimulating antibodies) Nodular Goitre (older people) Hyperemesis gravidarum Post partum thyroiditis Post viral thyroiditis Drugs (amiodarone)
Cause of hyperthyroidism with high TSH
Resistance to thyroid hormone
Drugs (amiodarone, heparin)
TSH secreting pituitary adenoma
Neonatal period
Signs/Symptoms of Hyperthyroidism
Heat intolerance and sweating Bulging eyes irregular Periods Fatigue Weight loss (increased appetite) Increased bowel movements Palpitations Tremor Poor concentration
Treatment of mild hyperthyroidism
Propanolol
Why is Propanolol used in treatment of mild hyperthyroidism?
Blocks action of catecholamines (which is increased by XS cortisol)
Non-specific, acts on all cells in the body
Treatment of Graves disease
Antithyroid medications
(Radioactive Iodine - isolation, not good for families)
Thyroidectomy
Treatment of nodular goiters/adenomas causing hyperthyroidism
Radioiodine therapy
Why does Addison’s Disease cause hyperpigmentation?
High ACTH
Gives rise to MSH
Stimulates melanocytes
Why does Addison’s Disease cause anorexia?
High ACTH
Gives rise to MSH
Inhibits appetite
Signs/Symptoms of Addison’s disease
Hyperpigmentation Anorexia/Weight loss Hyperkalaemia Hyponatraemia Weakness and fatigue Sexual dysfunction Hypotension Dehydration
Causes of Addison’s Disease
Granulomas in adrenals (sarcoidosis, TB, fungal infection) Shrunken adrenals (Autoimmune Adrenalitis, IDDM, Metastatic cancer Secondary to pituitary problem
Plus Amyloidosis and Haemochromatosis
Lab findings in Addison’s Disease
Hyperkalaemia Hyponatraemia Low cortisol High ACTH = primary Low ACTH = secondary
Synacthen Test
Measure serum cortisol
Administer Synacthen and wait 60 minutes
Measure serum cortisol
Normally, serum cortisol should double in 60 minutes
Treatment of Addison’s Disease
Cortisol replacement - Hydrocortisone
Aldosterone replacement - Fludrocortisone
Causes of Cushing’s Disease
Pituitary tumour (secreting ACTH)
Drugs - exogenous corticoids
Adrenal adenoma/carcinoma (secreting Cortisol)
What is Cushing’s Syndrome?
Hypercortisolism
Symptoms of Cushing’s Syndrome specific to men
Erectile dysfunction
Decreased libido and fertility
Signs/Symptoms of Cushing’s Syndrome
Weight gain/Obesity Fatty deposits (moon face and hump back) Thin skin (bruises easily) Increased thirst and urination Fatigue
Complications of Cushing’s Syndrome
Increased risk of infection T2DM Bone loss/fracture Kidney stones Enlargement of pituitary tumour Hypertension (A and NA cause vasoconstriction)
What is pheochromocytoma?
Rare tumour of adrenal gland tissue
5Ps of Pheochromocytoma
Pressure (Hypertension) - 90% Pain - 80% Perspiration - 71% Palpitation - 64% Pallor - 42%
Classic Triad of Pheochromocytoma
Palpitations
Perspiration
Pain
Absorptive state occurs
0-4 hours after a meal
Processes which occur during absorptive state:
TAG synthesis
Glycogenesis
Glycerol synthesis
Protein synthesis
How does pancreatic glucokinase differ from other hexokinases?
Not inhibited by its product - Glc-6-P
GLUT2
Glc transporter found in liver and pancreas
Low affinity
Works at high [Glc]
Glucokinase
Glc –> Glc-6-P
Where is UDP-glucose phosphorylase located?
Liver
UDP-Glucose Phosphorylase
Glc-6-P –> UDP Glc
PP-1 is activated by:
Insulin
Effect of PP-1
Upregulates glycogen production
Downregulates glycogenolysis
GLUT4
High affinity glucose transporter
Found in adipose tissue and muscle
Works at low [Glc]
Lipoprotein lipase
Cuts fatty acids from TAGs and transports them across capillary wall into cells
Lipoprotein Lipase is found in which cells
Luminal surface of capillary cells
Function of brown fat
Thermoregulation,
Protection against metabolic disease
Effect of exercise on GLUT4
Increase in number
GLUT4 is activated by:
Insulin
Function of carnitine shuttle
Allows Acetyl CoA to cross mitochondrial membrane so that it can enter the TCA cycle
Anabolism
Construction - consumes energy
Catabolism
Destruction - releases energy
Amino acids and glucose delivered to liver via
Hepatic Portal Vein
How do dietary TAGs reach the bloodstream?
Packaged into chylomicrons
Enter lacteals
Pass through thoracic duct into bloodstream
Action of insulin during Absorptive State
Uptake of amino acids and glucose into tissues
Uptake of TAGs into adipose tissues
Conversion of glucose to glycogen (activates glycogen synthase)
Action of glucocorticoids in post-absorptive state
Breakdown of protein and TAGs into glucose
Action of epinephrine in post-absorptive state
Breakdown of protein, glycogen and TAGs into glucose
Action of glucagon in post-absorptive state
Breakdown of glycogen into glucose
When does the body enter post-absorptive state?
After absorptive state
When enterocytes stop supplying portal hepatic circulation with glucose.
pK of a buffer
pH at which the buffer works best to resist changes in either direction.
Buffers found in renal tubules
Phosphate
Ammonia