Steroid Hormones Flashcards
(28 cards)
Human steroids derive from
dietary steroids or lanosterol made from acetyl-CoA in the liver
Lanosterol is made
in the liver (multistep at ER) from Acetyl-coA
What is the most abundant steroid?
Cholesterol
Where is cholesterol found in the body?
free in membranes and as esters in internal forms (liver, lipoproteins, atherosclerotic plaque)
What are the corticosteroids?
glucocorticoids (cortisol) and mineralocorticoids (aldosterone)
What is the primary role of glucocorticoids?
Regulate metabolism and immune function
What is the primary role of mineralocorticoids?
Maintain blood volume and control renal excretion of electrolytes
What are the sex steroids?
Androgens, oestrogens, and progestagens
What is the primary role of the sex steroids?
Produce sexual differences and support reproduction
Where are oestrogen and progesterone primarily made?
In the ovary and the placenta during pregnancy
Where is testosterone primarily made?
In the testes
Testosterone is converted to
oestrogen; regulates supply of each in both males and females
What is the rate-limiting step of sex steroid synthesis?
Conversion of cholesterol to pregnenolone (occurs in mitochondria)
How do anabolic steroids increase muscle and bone synthesis?
Interacting with androgen receptors
How do sex steroids change gene expression?
travel on sex-steroid-binding-globulin; free sex steroids cross the membrane and enter the nucleus where they find their receptor; receptor binds to a hormone response element and initiates transcription
How do adrenal steroids (mineralocorticoids and glucocorticoids) change gene expression?
travel through membrane and find receptor in cytosol; activate receptor by knocking off a heat shock protein; the activated receptor enters the nucleus, finds its hormone response element, and initiates transcription
Cyproterone
synthetic steroid inhibitor of the androgen receptor; blocks mRNA synthesis for androgenic proteins - can be used in testosterone cancers (ie prostate)
Side chain cleaving enzyme
in the mitochondiron, cleaves cholesterol to pregnenolone (a progesterone precursor to steroid hormones)
How do glucocorticoids suppress immune and inflammatory responses?
suppress cytokine synthesis: they bind a receptor in the nucleus that produces IkBa, the inhibitor of NF-kB that is bumped off by TNF to produce cytokines; tf production of IkBa blocks NF-kB from producing cytokines and activating the immune response
Dexamethasone
potent synthetic glucocorticoid used as an anti-inflammatory and immunosuppresant
Beclomethasone
analogue of dexamethasone, used as a nasal spray for allergies
Prednisolone
used in severe asthma
FSH in males
spermatogenesis and growth of seminiferous tubules
FSH in females
production of ova, estradiol (estrogen), and development of follicles
