Repro Physl 2 Flashcards
What is Cholesterol the main synthesis for?
The sex hormones
What does Aromatase do?
Converts progesterone to Estrone a type of estrogen
What does Aromatase do?
Converts testosterone to Estradiol
What does 5-alpha reductase do?
Converts testosterone to DHT which is more potent
What kind of actions do the Androgens typically have?
Masculinizing actions
What is an example of an androgen?
Testosterone
What are the Androgens mostly synthesized by?
The testes
Where does other androgen synthesis occur?
In the adrenal cortex
What is the difference between adrenal source androgens and testes androgens?
Adrenal source androgens tend to be less potent than testosterone
What is the issue with adrenal gland androgens?
They are not potent enough to maintain normal reproductive function
Where are androgen produced in women?
In the adrenal glands
Can androgens be produced in ovaries?
Yes but in small amounts
What is DHT?
A more potent form of testosterone synthesized by 5-alpha-reductase
Where are most estrogens produced in females?
The ovaries
What is the prominent circulating form of estrogen in women of reproductive age?
Estradiol
What is Estrone?
The prominent estrogen in post menopausal women
What is Estriol?
The prominent estrogen found in pregnant women produced by the placenta
What do estrogens require to become estrogens?
They need to be produced from androgens via aromatization
What does Enzyme aromatase do?
Facilitates the transition from androgens to estrogens
Where are estrogens in males released?
From the testes and in non-gonadal tissues like the brain, skeletal muscle, and adipose tissue
Which tissues possess aromatase in males to convert androgens to estrogens?
Adipose tissue, brain, skeletal muscle
What is Progesterone produced by?
The ovaries
Which phase of the menstrual cycle is progesterone produced?
The luteal phase
What is the precursor of progesterone in males?
Pregnenolone
In addition to the ovaries, where can progesterone also be procued?
The adrenal glands
What hormones does the placenta produced?
Estrogen and progesterone
What is the solubility of gonadal hormones?
They are lipid soluble so they can diffuse easily into cells
What do Gonadal steroid hormones do once they diffuse into a cell? (classical pathway)
They bind to the receptor and form a hormone-receptor complex which binds to DNA and modify mRNA formation leading to the modification of protein synthesis and alter circulating protein levels
What are the characteristics of the non-genomic pathway of Gonadal Steroids?
- More rapid
- Different receptor
- In various tissues
What are the Gonadal Steroid important for?
- Development of accessory reproductive organs
* Development of secondary sex characteristics
What are the accessory reproductive organs?
- Duct system carrying sperm or eggs
* Breast development
What are Secondary Sexual Characteristics?
- Phenotypic difference between males and females
- Hair distribution
- Body shape
- Height
What produces Gonadotropin-releasing hormone (GnRH)?
The Hypothalamus
Where does GnRH go from the hypothalamus?
The hypothalamic-pituitary portal vessels to the anterior pituitary
Which portion of the pituitary does GnRH act on?
The anterior pituitary
What is the source of GnRH?
The neuroendocrine cells in the hypothalamus
How does GnRH affect the anterior pituitary?
It stimulates the release of FSH and LH
Where do FSH and LH go from the anterior pituitary?
They go into the circulation and act on the Gonads
How do FSH and LH affect the gonads?
Facilitates the production of sex hormones and support gametogenesis
Where does the stimulation of the production of sex hormones by FSH and LH act?
Anywhere in the body with estrogen and androgen receptors
What has a negative feedback on GnRH?
The production of sex hormones and FSH and LH
How do sex hormones affect FSH and LH release?
Testosterone has a negative feedback effect on the anterior pituitary. And estrogen can have either a positive or negative feedback effect
How does impaired function of the hypothalamus or anterior pituitary affect gonadal steroids and gametogenesis?
It causes failure to secrete gonadal steroid and gametogenesis
What does LH tend to act on and what does it do?
The endocrine cells of the gonads (ovaries or testes) and causes them to produces steroid and peptide hormones
What does FSH tend to stimulate?
Gamete production
What is the dual role of LH in females?
It plays a role in gamete production and stimulates endocrine cells to produces steroid and peptide hormones
What happens if there is not enough LH?
Ovulation cannot happen
Which levels of estrogen have negative feedback effects?
Low-moderate levels
What kind of feedback do high levels of estrogen have?
It has a positive feedback effect
What is the pattern of GnRH release?
It has pulsing release every 1-3 hrs
What is the pulse of GnRH followed by?
A pulse in FSH and LH
What is the GnRH pulse generator?
The region of the hypothalamus responsible for producing GnRH
Why is GnRH released in pulses?
Because steady high levels down-regulates the receptors on gonadotropin cells in the pituitary
How does a GnRH agonist affect cancer cells?
It slows the growth the cancer cells by down regulating the receptors
Where do GnRH neurons receive input?
Other brain regions or circulating hormones
What does kisspeptin do?
Controls the pulsatile pattern of the GnRH neurons
What hormones are located upstream of GnRH neurons?
Kisspeptin neurons
What is kisspeptin responsible for initiating?
Puberty
What kind of feedback can things have on kisspeptin neurons?
sex hormones can have negative or positive feedback on kisspeptin neurons
What is the regulation of LH and FSH release by sex hormones in addition to?
Inhibins
Where are inhibins produced and what they do?
They are produced by the gonads and contribute to the control of gonadotropin release and FSH release from the anterior pituitary
What is reproductive function in females affected by?
- Stress
- Nutritional status
- Daylight cycle
- Environmental estrogens
How does Melatonin affect GnRH production?
It tends to inhibit GnRH production
Why are environmental estrogens bad?
Because they act in the body the same way that estrogens do and bind to estrogen receptors or they may be anti-estrogenic
Where can environmental toxins accumulate?
In fat tissue
