Steroids Flashcards
Where are steroid hormones primarily synthesized?
Adrenal Cortex-adrenocorticoids
Ovaries and testes-Sex steroids
What is steroid secretion controlled by?
Peptides secreted from the hypothalamus and pituitary
What are the effects of glucocorticoids?
Modulation of carbohydrate metabolism by increasing levels of glycogen in the liver and blood glucose, stimulate immune system (initial), immune suppression and cells death (prolonged)
When does basal rhythmic secretion of glucocorticoids increase?
During periods of stress
What are the effects of mineralcorticoids?
Promots Na uptake, modulates K transport, control of water reabsorption
When are mineralcorticoids secreted?
Only during periods of stress
Secretion of what is essential for life?
Cortisol
What occurs in the evening?
Hypothalamic activation releases corticotropin releasing hormone which stimulates the pituitary to make ACTH which stimulates the adrenal gland to make cortisol
At what time of day are corticosteroid levels the highest?
The morning
What occurs during stress?
Stress gives a bigger stimulation of the limbic system, causing more CRH, more ACTH and thus more cortisol. It also stimulates inflammaory and immune systems which releases interleukins with stimulates CRH and ACTH
What is the negative feedback loop in the case of stress?
Cortisol has negative feedback on the hypothalamus, pituitary and inflammatory and immune systems to prevent secretion of CRH and ACTH
What happens if you take long term steroids?
Your ability to produce endogenous steroids is compromised, thus your ability to combat stress in reduced.
Prolongation of treatment increases the incidence of disabling or life threatening effects
What is the major building block in glucocorticoid synthesis?
Cholesterol
What increases cortisol levels in the body?
Stress, hypothydroidsim and liver disease
What does corticosteroid-binding globulin (CBG) do?
Binds about 90% of the circulating cortisol, inactivating it. Can reach a point of saturation, increasing free cortisol levels
Only free or loosely bound to albumin are available to work.
What increases CBG levels?
Pregnancy, estrogen administration, hyperthyroidism
What decreases CBG levels?
Hypothyroidism, genetic defects in synthesis and protein deficiency states
What do synthetic corticosteroids bind to?
Those like dexamethasone are largely bound to albumin rather than CBG
How do the steroids work on the cell?
Cross the cell membrane and bind to the glucocorticoid receptor which is transported by HSP90 proteins to the nucleus. The steroids dimerize, move into the nucleus and binds to the glucocorticoid response element which increases transcription of anti-inflammatory proteins.
How do NF-kB activating signals work on the cell?
The signals bind to the receptor on the cell. Proteins (p65 and p50) dissociate from the receptor and bind to response elements to inhibit steroid binding to the element and prevent transcription of pro-inflammatory proteins
No pre-mRNA
What causes decreased transcription?
Inflammatory cytokines, chemokines, inflammatory enzymes, inflammatory proteins, mediator receptors, adhesion molecules
What accounts for the more rapid effects of glucocorticoids?
Non-genomic activation of anti-inflammatory proteins
Which topical corticosteroids are used for dermatologic use?
Ultra high potency: Clobetasol
High: Desoximetasone, Amcinonide
Medium: Betamethasone, Triamcinolone
Low: Desonide, Hydrocortisone
How can the vehicle of topical corticosteroids affect its potency?
Ointments have higher potency than cream or lotions
