PH1124 - Reproductive hormones Flashcards
what is a hormone? (2)
- chemical substance produced by ductless glands within the endocrine system
- often then secreted directly into bloodstream
what molecule hormones mostly derived from?
- most hormones derived from cholesterol
what are the physiological functions of hormones? (6)
- reproductive cycle; lactation
- growth and development
- metabolism
- digestion
- sleep
- stress and mood (brain)
- reproductive cycle; lactation
- growth and development
- metabolism
- digestion
- sleep
- stress and mood (brain)
- are synthesized and secreted at different levels throughout a person’s lifetime
- increasing at puberty and normally decreasing with old age
- feedback mechanisms regulate these hormones
what are the main modes of action for hormones? (3)
- endocrine action
- paracrine action
- autocrine action
what is the endocrine action of hormones? (2).
- hormones are secreted from a secreting cell in the ductless gland directly into the circulatory system
- they act on distant cells/organs via their target receptors
what is the paracrine action of hormones?
- hormones are secreted and then diffuse through the interstitial spaces to act on nearby target cells
what is the autocrine action of hormones?
- hormones act on the same cell that secreted them via their receptors
what is the endocrine system? (2)
- collection of glands located throughout the body that manufacture and secrete hormones to regulate physiological functions
- generally act in a paracrine or endocrine manner
what are the major endocrine glands? (4)
- adrenal gland
- hypothalamuc
- ovaries and testes
- pituitary gland
what are the general classes of hormones derived from different building blocks? (3)
- hormones derived from amino acids
- protein and peptide hormones
- hormones derived from lipids
what is the structure of cholesterol? (3)
- 3 cyclohexane rings (A to C)
- 1 cyclopentane ring (D)
- large 6C hydrocarbon side chain (C22 to C27)
what is cholesterol the precursor for the biosynthesis of? (4)
- vitamin D
- bile acid; lipid digestion
- steroid hormones; adrenal steroids, glucocorticoids, mineralocorticoids
- sex steroid hormones
where are reproductive steroid hormones mainly produced? (2)
- produced mainly by the gonads (ovaries or testes)
- some production by placenta and adrenal glands
what are reproductive hormones soluble in? (3)
- they are water-insoluble but are lipid soluble
- can easily move across the plasma membrane but not stored in the body
- bound to the carrier steroid hormone-binding globulin
(SHBG) during transport in the bloodstream
what are the classes of reproductive steroid hormones? (3)
- oestrogens
- androgens
- progestogens
how are reproductive steroid hormones produced?
- produced through the metabolic process called steroidogenesis
what do reproductive steroid hormones specifically interact with?
- oestrogen (ER), androgen (AR) or progesterone (PR) receptors to exert their effects
what are the types of oestrogen reproductive
steroid hormones? (3)
- oestradiol
- oestriol
- oestrone
what are the types of androgens reproductive
steroid hormones? (3)
- testosterone and 5a-dihydrotestosterone (DHT)
- androstenedione
- dehydroepiandrosterone (DHEA)
what are the types of progestogens reproductive
steroid hormones?
- progesterone
what is the potency of DHT?
- DHT is a metabolite of testosterone and is a more potent androgen than testosterone as it binds more strongly to androgen receptors
what are the precursors for all reproductive
steroid hormones? (2)
- cholsterol
- pregnenolone
what is the main site for progesterone synthesis? (2)
- in the ovaries (corpus luteum cells)
- in the placenta during pregnancy
what is the main site for testosterone synthesis? (3)
- testes; leydig cells
- ovaries; theca cells
- adrenal gland, prostate gland and placenta
what is the main site for estradiol synthesis? (3)
- ovaries (granulosa cells)
- placenta
- adipose tissue in breast
what is the main site for oestrogen synthesis?
- ovarian granulosa cells
what is the main site for androgen precursor synthesis?
which in turn are converted into oestrogen by the granulosa cells
- ovarian theca cells
what is the corpus luteum?
- corpus luteum develops from ovarian follicle during the luteal phase of menstrual cycle after ovulation
how is progesterone made by the placenta?
- by the placental syncytiotrophoblasts [SYN] surrounding the placental villi
what is the primary role of the reproductive system? (2)
- to support gametogenesis; oogenesis in women and spermatogenesis in men
- to cause maturation of the reproductive organs, underpin fertility and pregnancy
what is the secondary role of the reproductive system?
- drive development of male or female physical characteristics
what are the effect on androgen on the body? (2)
- maturation of the sex organs and deepening of the voice
- growth of pubic and axillary hair in pubic regions/underarm
why are circulating levels of testosterone important for the effects of androgens?
- peaking post-puberty but present into late adulthood
what are the anabolic effect of androgen in the body? (3)
- growth of muscle mass and strength
- increased bone density and strength
- stimulation of linear growth and bone maturation
what is androgen clinically used to treat? (3)
- delayed puberty caused by androgen deficiency (in males)
- hypogonadism causes diminished production of androgens by gonads (in males)
- Hot flushes (in females)
what are the side effects of clinically using androgen? (3)
- early use of androgens for treating delayed puberty can lead to premature closure of epiphysis of long bone, resulting in short stature
• can cause acne (androgen’s impact on skin’s sebaceous glands)
• FDA report (2014); increased incidence of cardiovascular disease can be associated with testosterone replacement therapy
what is the role of oestrogen on the body?
- regulate growth (proliferation & cell survival) by altering expression of many genes in tissues that express the ER
what are the effects of oestrogen on the female body? (4)
- increasing growth and development of the breast and uterus
- broadening of the pelvis and also favours bone formation
- gain of further female secondary sexual characteristics eg. growth of axillary hair
- impact on adipose tissue & muscle mass
what is oestrogen clinically used to treat?
- Hormone Replacement Therapy (HRT) after menopause
what are the side effects of clinically using oestrogen? (3)
- a very slightly increased risk of breast cancer with certain HRT strategies
