biochemistry 8 Flashcards
what is the negative feedback loop in the endocrine system
neural/ chemical stimulus –> endocrine organ –> hormone –> target organ —> biochemical/ physiological effect
how is cortisol produced in the body
1) hypothalamus secretes CRH
2) CRH stimulates anterior pituitary gland to release corticotropin (ATCH)
3) corticotropin stimulates adrenal cortex cortisol production by:
1) - Corticotropin interacts with G-protein-coupled receptors
2) Stimulates cAMP production
3) Activates cholesterol esterase
4) Cholesterol esters → FFA + Cholesterol
5) Cholesterol –> Cortisol
how is negative feedback used in the production of cortisol
- cortisol from adrenal cortex suppresses CRH and ATCH secretion
how is testosterone produced In the body
1) hypothalamus secretes gonadotropin releasing hormone (GnRH)
2) GnRH stimulates pituitary FSH and LH release
3) LH stimulates Leydig Cell Testosterone production via
1) LH interacts with a G protein–coupled receptors
2) Increase cAMP → Activate PKA
3) Activates cholesterol modifying enzymes
4) Cholesterol –> Testosterone
how is negative feedback used in testosterone production
- testosterone from leydig cells suppress secretion from hypothalamus and pituitary
- extra negative feedback of pituitary by FSH and testosterone stimulated sertoil cells and inhibin
how is oestradiol produced in the body
1) hypothalamus secretes GnRH
2) GnRH stimulates pituitary FSH and LH release
3) FSH stimulates ovarian E2 - oestradiol production
4) LH levels stimulate ovulation
how is negative feedback used in E2 production
- E2 secreted by ovaries suppresses secretion from hypothalamus and pituitary
- extra negative feedback of pituitary by E2 stimulated follicle inhibin release
what are the 5 main classes of signalling molecules and how are they used in the body
- progestogen - prepare muscles for implantation and supports pregnancy
- androgens - male sexual behaviours and lean muscle mass
- oestrogen - female sex characteristics
- glucocorticoids - glucose and glycogen synthesis and inhibits the inflammatory response
- mineralocorticoids - regulates salt balance and blood volume and pressure
how is cholesterol synthesised into pregnenolone
- Cytochrome P450 enzymes (CYP) catalyze two hydroxylations (OH)
- Requires NADPH
- Cleaved by cholesterol 20,22-desmolase
how is pregnenolone converted into various steroid hormones
via hydroxylation and Lyase Glucocorticoid to Androgen
what occurs when oestrogen binds to an oestrogen receptor
- has zinc based DNA binding domains
- binds to oestrogen response element on DNA
- ligand binding causes a structure change
- structure change enables transcriptional regulator recruitment
- coactivators stimulate transcription
what does tamoxifen do
- anti cancer drug
- inhibits cell growth
- bind to the pocket normally occupied by estradiol
- tramoxifen extends from this pocket
what ate the causes, symptoms and treatment of cushings syndrome
causes - cortisol over production or exposure
symptoms - obesity, high blood pressure, high blood sugar, skin bruises easily, muscle weakness
treatment - remove source of cortisol
what are the causes, symptoms and treatment o Addisons disease
causes - low aldosterone and cortisol due to an autoimmune disorder and adrenal gland disfunction
symptoms - weight loss, fatigue, abdominal pain, dark parches on skin, low blood pressure
treatment - aldosterone and cortisol hormone replacement
what is the causes, symptoms and treatments of androgen excess
causes - high androgen from polycystic ovaries
symptoms - irregular periods, excess hair growth, weight gain, thinning hair oily skin or acne
treatment - antiandrogens
what are the causes, symptoms and treatments of congenital adrenal hyperplasia
causes - glucocorticoid deficiency
symptoms - increased androgen causing enlarged adrenal gland, atypical genitalia, body less able to deal with stress, poor salt retention
treatment - cortisol/ aldosterone HRT, genital surgery, salt supplements
what are the causes, symptoms and treatments of menopause
causes - decreased oestrogen - hypothalamus related from inhibitory influences, pituitary activity increases which increases FSH and LH
symptoms - end of menstruation, unpleasant physical and emotional symptoms
treatment - oestrogen and progesterone replacement. increase calcium to reduce bone loss
what are agonists
activates nuclear hormone receptors
what are antagonists
inhibits nuclear hormone receptors
what are the two main classes of steroid hormones
- corticosteroids
- anabolic steroids
what are corticosteroids and how do they work
- artificial version of adrenal gland hormone
- reduces immune system activity and decreases inflammation
what are corticosteroids used to treat
- Asthma
- Chronic obstructive pulmonary disease
- Hay fever, hives and eczema
- Pain
- Inflammatory bowel disease
e.g. Crohn’s disease - Lupus
- Multiple sclerosis (MS)
what are anabolic steroids and what are the used for
- synthetic hormone that mimics testosterone
- promotes an increase in muscle size
what are anabolic steroids used to treat
- Hormone problems in men
- Delayed puberty
- Muscle loss from disease
what are the high dosage dangers of anabolic steroids
- Acne, increase aggression, mood swings, paranoia
- In males; decrease libido, decrease testicle size and lower sperm counts.
- In females; increase libido, loss of breasts, facial hair growth, hair loss, irregular periods.
- High cholesterol, increase heart attack/strokes, Liver and kidney problems
