128 - Endocrine Flashcards
What are the 4 ways signals are sent in the endocrine system?
Autocrine (to same cell)
Paracrine (to neighbours)
Endocrine (via bloodstream)
Neurohormones (from synapses, via bloodstream)
What are the 4 types of hormone?
Peptide
Amino acid/amine
Steroid
Fatty acid derivatives
How are peptide hormones produced?
Encoded by a gene, preprohormone gets made, modified in the ER, then turned into a prohormone in the golgi, then processed into the active hormone and packaged into secretory vesicles.
Which hormone type is water soluble?
Peptide hormones, amino acid derivatives
Which hormone type is lipid soluble?
Steroid hormones
What makes up amine hormones?
Derived from thyroside
What makes up steroid hormones?
Derived from cholesterol
What subtypes of steroid hormones are there?
Glucocorticoids - cortisol
Mineralocorticoids - Aldosterone
Sex steroids - testosterone, Oestrogen, Progesterone
What makes up fatty acid derivatives?
Polyunsaturated fatty acids
- eg. Eicosanoids - prostaglandins
What is the mechanism of action of water soluble hormones?
They can’t cross cell membrane, so bind to a specific receptor, use a secondary internal messenger which alters cell function and exerts the physiological effects needed.
What is the mechanism of action of Lipid soluble hormones?
They can diffuse through the cell membrane, bind to nuclear receptors directly, form an activated hormone receptor complex which causes specific protein production and exerts the physiological effects needed.
What is chronotropic control?
Endogenous neuronal rhythmicity - causes diurnal rhythms and sleep wake cycles..
Describe the hypothalamic-pituitary-adrenal axis
Hypothalmus produces CRF, acts on anterior pituitary - produces ACTH - acts on adrenal cortex - produces cortisol.
(cortisol has negative feedback against hypothalamus and pituitary)
What effect does cortisol have on the body?
Stress response
Increase blood glucose
Reduce the immune system
Reduce protein synthesis
What disease is caused by excess cortisol production?
Cushing’s syndrome
What are the causes of Cushing’s syndrome?
Iatrogenic (give to much cortisol)
Primary Cushing’s - Excess cortisol production, eg. adrenal tumour
Secondary Cushing’s - Excess ACTH causing increased cortisol production, eg. pituitary tumour, cushing’s disease.
What re the features of Cushing’s / excess cortisol?
Moon face Central adiposity Hirsutism Depression High blood sugar High BP Fatigue Immunosuppression Leg oedema If cause is high ACTH - skin pigmentation.
What investigations would you do if you suspected Cushing’s?
24hr urinary cortisol levels - high
ACTH levels - low=primary disease, high=secondary disease
Dexamethasone suppression test - give low dose at midnight, should suppress cortisol production in the morning. In Cushing’s it doesn’t.
What can be given to treat Cushing’s?
Metyrapone - inhibit synthesis of cortisol
Look into removing tumour if cause?
What is adrenal insufficiency?
Insufficient production of cortisol
= Addison’s disease
What can cause adrenal insufficiency?
Sudden withdrawal of long term steroids
Addison’s - primary adrenal insufficiency, can be autoimmune of TB.
What are the features of adrenal insufficiency?
Pigmentation (as compensatory high ACTH) Malaise Nausea Vomiting Low blood glucose hypotension Weight loss
What is an addisonial crisis?
Often the first presentation of addison’s
Causes collapse, very low BP, Low blood sugar.
Can be fatal
What investigations would you do if you suspected adrenal insufficiency?
ACTH infusion - you would see an inadequate cortisol response
Measure blood - high basal ACTH, high K+, low Na+, low blood glucose