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REPRODUCTIVE HORMONES (STEROIDS: Derived from cholesterol (Estrogens…
REPRODUCTIVE HORMONES
STEROIDS: Derived from cholesterol
Estrogens
Estadoil
Uses: Development of Secondary female characteristics, regulation of menstrual cycle,
Androgens
Testosterone 50%, 2-3dihydrotestosterone (DHT) 100%, DHEA 4%, Androstenodione 8%,
Uses: development of male secondary sex characteristics, genitalia growth, larynx growth, pubic and axillary hair, increased sexual acts and thoughts, increased labido,
Progestagens
Progesterone 100%, 17a hydroxyprogesterone, 40-70%, 20a hydroxyprogesterone 5%
Uses: gestation, supports endometrium, evolves mamillary glands
Steroids must takes a metabolic pathway when synthesising from cholesterol into other hormones with the use of enzymes
Lipophillic: diffuse through the phospholipid bilayer and binds to intranucleur receptors
PROTEINS AND PEPTIDES: Chains of 3-200+ amino acids
Gonadotrophins
LH: from AP. acts of testis (leydig cells) and ovary (thecal, luteal and granulosa cells). Made up of Achain of 92aa and 2 carbohydrate chains + Bchain of 121 aa and 2 carbohydrate chains
FSH: From AP. Acts on sertoli cells and granulosa cells. Made up of Achain of 92aa and 2 carbohydrate chains + Bchain of 111 aa and 2 carbohydrate chains
Human chorionic gonadotrophin (hCG) from syncytiotrophoblasts. Acts on luteal cells in the ovary and leydig cells in the fetak testis. Made up of Achain of 92aa and 2 carbohydrate chains + Bchain of 145 aa and 2 carbohydrate chains
Cytokines
Polypeptides with one or two chains, grouped into families on basis of molecular structure
Inhibin: effects granulosa cells and sertoli cells: intraovarian and intertesticular activity, gonad-pituitary interactions
Anti Mullarian hormone: causes the regression of the mullarian ductS = responsible for the development of male genitalia, descent of the testis, inhibits growth of early follicles
Relaxin: corpus luteum, partuation(ripening of the cervix), separation of pubic symphysis for assistance in child birth
Small peptides (oligopeptides) 3-10aa
Synthesised in form of larger polypeptide precurser
Active cleaved prior to secretion
Gonadotrophin releasing hormone: neurosecretory cells of hypothalamus, controls the release of gonadotrophins
Oxytocin: from hypothalamus stored in posterior pituitary gland. Is involved in parturition, milk led down and bonding.
Kisspeptin: neuropeptide from hypothalamus, controls GnRh and fertility
Somatomammotrophins
Are responsible for tissue growth and function
Large single peptide chains (191-199aa)
Prloactin: acts on mammary glands (lactation) and hyperprolactinemia supresses fertility
Human chorionic somatommotrophin (hCS): made from syncytiotrophoblasts, mobilizes fatty acids during pregnancy
Growth hormone: from AP is responsible for puberty and growth
Hydrophillic: Bind to receptors on the membranes surface which causes a secondary messenger to diffuse into the cell and influence/have the desired effect
Determinants of Hormone Action (4)
2. Blood concentration: Production rate/ clearance rate
The presence of binding sites also determines hormone levels in the blood. Hormones may also be metabolized in their target tissues = enzymatic conversion of circulating hormone by target cell into a more usable form eg, testosterone to 5a-dihydrotestosterone
1. Transport:
Protein hormones
are hydrophillic, they bind the receptors on the cell membrane and cause a secondary response to diffuse into the cell and carry out the response.
Steroid hormones
: are hydrophobic, they enter the target cell via the membrane and bind to intranucleur receptors.
Carrier proteins:
being bound or unbound determines its effects (hormone can only have an effect if not already bound to another receptor; as they aren't "biologically active".)
4. Receptor expression
Down regulation
: high receptor density (strong response) = reduced receptor density ( decrease sensitivity) = diminished response
Up regulation:
low receptor density (weak response) = increased receptor density (increased sensitivity) = stronger response. Closely related molecules can bind to the same receptor, these can be antagonists (decrease response) or agonists (increase response)
3. Secretion Patterns:
Different secretion patterns alter the actions of a hormone.
Pulsatile
: secreted in bursts.
Circadian
: secreted ones daily.
Infradian
: less than once daily.
Circannual
: once yearly.
Circhoral
: once hourly.
Ultradian
: more than once daily.
Diurnal:
once daily
EICOSANOIDS: Derived from arachidonic acid
Postaglandins is the main reproductive group
Aspirin blocks synthesis of PG (good for cramps)
Paracrine secretion
synthesised by seminal vesicle, myometrium, cervix (important for parturition)
Hormones: chemical messengers.
Endocrine
: into blood stream.
Exocrine:
into a duct or tube.
Paracrine:
adjacent/local cells, eg. leydig cells.
Autocrine
: affects the tissue which releases it eg. granulosa cells.
Slow release, wide spread, long lasting effects
3 Types: Steroids, Protiens and eicosanoids