Steroid hormones Flashcards
What are human steroids derived from?
Dietary steroids or made from acetyl-CoA in liver
What is the most abundant steroid?
Cholesterol
What do corticosteroids include?
Glucocorticoids and mineralocorticoids
Where are oestrogen and progesterone made?
Ovary
Placenta during pregnancy
Where is testosterone made?
Testes
Describe the effect of anabolic steroids?
Interact with androgen receptors to increase muscle and bone synthesis
Describe the pathway for the production of cholesterol from acetyl-CoA in the liver?
How are steroids eliminated from the body?
Oxidation by cytochrome P450
Most significant pathway involves CYP3A4 in liver ER
Introduces -OH into steroid ring
Describe how steroids exert their effects on target tissues?
Enter cells > bind internal receptors > steroid-receptor complex binds at Hormone Response Elements in DNA > gene expression altered
Describe the function of the nuclear androgen receptor?
Allows male sex steroids to meidate the male phenotype
What is cyproterone acetate?
What is it used for?
Synthetic steroid inhibitor of androgen receptor > blocks synthesis of mRNA for androgenic proteins
Used to treat hirsutism in females, and as part of hormone therapy for male-to-female gender change
List the steroids released from the layers of the adrenal cortex?
List the secretion signal for each?
Zona reticularis: DHEA (signal is ACTH)
Zona fasiculata: cortisol (signal is ACTH)
Zona glomerulosa: aldosterone (signal is Ang II/III and ACTH)
What is DHEA?
Describe its function?
Testosterone-like
Various protective effects of adrenal cortex
Weak androgen
Which hormones have mineralocorticoid function?
Aldosterone
Progesterone
Deoxycortisone
Describe how mineralocorticoids exert their effects on target tissues?
Bind cytosolic mineralocorticoid receptor > translocate into nucleus > alter gene expression
Describe what happens to mineralocorticoid receptors when hormone is not bound?
Receptors bind heat shock proteins to prevent transcription of targeted genes
Describe the effects of cortisol?
Stimulates protein breakdown to amino acids
Inhibits protein synthesis
Stimulates gluconeogenesis
Inhbits utilisation of glucose by adipose tissue
Facilitates lipolysis in adipose tissue
Stiulates appetite > weight gain
Which hormone opposes cortisol?
DHEA
How do glucocorticoids suppress immune and inflammatory responses?
Suppress cytokine synthesis
What is dexamethasone?
What are its actions?
Potent synthetic glucocorticoid
Acts as an anti-inflammatory and immunosuppressant
Which steroid is used in the treatment of asthma?
Describe the side effects?
How shoud it be administered and removed as treatment?
Prednisolone
SEs: cataracts, osteoporosis, myopathy, fragile skin, easy bruising, hair loss, hirsutism, puffy cheeks, buffalo neck, weight gain
Should progressively reduce dosage rather than stop altogether (adrenals significantly reduce steroid production when levels are high and it takes a few weeks for them to recover)
What is leuprorelin?
What is it used for?
Analogue of GnRH > induces chemical castration via inhibition of FSH and LH release
Females: complete suppression of oestrogen and progesterone from ovaries
Males: complete suppression of testosterone from testes
List the sex steroids, their secretion signals and functions?
How are sex steroids transported in the body?
Bound to sex hormone-binding globulin (SHBG)
Describe the menstrual cycle in terms of hormones?
Describe the ovarian cycle in terms of generation of generation of hypothalamic releasing hormone, pituitary gonadotropic hormones and sex hormones?
Which hormone is used in pregnancy tests?
Human chorionic gonadotropin (hCG)
Where is testosterone produced?
Males: ore than 95% in Leydig cells in testes
Females: small quantities in ovaries and placenta
Zona reticularis of adrenal cortex produces in both sexes
What are the releasing and inhibiting signals for testosterone?
Releasing: LH
Inhibiting: FSH (inhibits LH)
Describe the role of sex steroids in prostate and breast cancer?
Growth of prostate and breast cancers remains dependent on sex steroids
Describe hormonal therapy in the treatment of prostate cancer?
Andorgen deprivation therapy > decreases production or blocks effect of testosterone
Leuprorelin> agonist of GnRH receptors > interrupts pulsatile stimulation > inhbits LH and FSH release
Describe hormonal therapy in the treatment of breast cancer?
Tamoxifen: oestrogen receptor antagonist in breast tissue
Letrozole: aromatase inhibitor
Describe the action of anabolic steroids?
Act on muscle mass: increase production of actin and myosin, block effects of cortisol > decreased catabloism of muscle > decreased recovery time, increase BMR > decrease fat
Describe the negative side effects of anabolic steroids?
Physical: liver damage, hypertension, jaundice, renal failure, acne
Psychiatric: delusions, jealousy, paranoia, irritability, feelings of invincibility
Men: reduced sperm count, shrinking testicles, infertility, prostate cancer, baldness
Women: baldness, facial hair growth, deep voice, menstrual cycle changes
