3. Male and female reproductive endocrinology Flashcards

1
Q

Testosterone

A

androgen which is secreted in response to LH secretion
Stimulates testes to cause sperm production
FSH also acts on testes to cause sperm production

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2
Q

What regulates testosterone secretion

A

In order for sperm production to occur there must be testosterone, and in order for testorone to be secreted there must be LH
Testosterone negative feedbacks to inhibit LH and FSH secretion
Inhibin also causes therapeutic feedback, but isn’t used therapeutically in males

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3
Q

Embryology reproductive endocrinology

A

In male embryo, testes secrete testosterone which causes development of male feotal/embryonic development

In the female, oestrogens have no effect and there is no testosterone, so females develop female anatomy

Default situation is female anatomy

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4
Q

Testosterone in puberty

A

Massive increase in testosterone secretion in puberty
Causes male secondary sexual characteristics

Once puberty starts, testosterone levels are maintained until about 40 when they decrease, but never stop

secondary sexual characteristics remain in males until they die

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5
Q

Secondary characteristics as a result of testosterone

A

Increased aggression and libido* - effects of testosterone on the brain
Enlargement of the larynx - voice breaks
Male pattern pubic hair - also facial hair, chest hair
Maturation of genitalia
Muscle development - due to anabolic steroids
Sperm production
Bone growth* - long bone growth - arms and legs
Acne - increased sebaceous gland activity

*some effects of testosterone require conversion to oestradiol by aromatase

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6
Q

Female reproductive endocrinology

A

GnRH causes LH and FSH release

LH and FSH cause ovulation - oestrogens and progesterone released
Progesterone and oestrogen negative feedback of GnRH

Oestrogens (e.g. oestradiol) to do with ovulation

Progesterone acts for and behalf of pregnancy
Progestogens are progesterone like hormones

Oestrogens negative feedback on FSH
Progesterone negative feedback on LH

In foetus, lack of male hormones (testosterone) results in female characteristics

In puberty, lack of male hormones result in secondary sexual characteristics. Usually around 11-12 until 17-18

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7
Q

Female secondary sexual characteristics

A

Bone Growth - long bone growth so increase in stature
Female psyche - more likely to have more caring type personality
Fair complexion
Breast Development
Widening of the pelvis
Maturation of genitalia
Female pattern pubic hair - no facial or chest hair growth
Subcutaneous fat deposition - instead of muscle growth caused by androgens
Ovulation and menstruation

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8
Q

Hormones during menstrual cycle

A

GnRH causes secretion of FSH and LH which cause oestrogen and progesterone secretion

First half of menstrual cycle is oestrogen dominant
Second half of menstrual cycle is progesterone dominant

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9
Q

GnRH secretion in females

A

In females, GnRH secretion is pulsatile and not constant, and the frequency of that pulsatile secretion determines whether you have FSH secretion or LH secretion.

It depends on number of GnRH secreted per day. This pulsatility depends on the part of the month, can be slow at one part or quick at another.

Slow production causes FSH production and rapid causes LH production.

In a female foetus with XX chromosome, the pulsatility of the hypothalamus is there before the baby is born. This means that duration of menstrual cycle is built into the feotus.

If a female feotus is exposed to testosterone or androgens, she loses the pulsatility of the GRH release, and becomes like a male

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10
Q

Menopause

A
At age 52 women stop secreting eostrogen etc and undergo loss of secondary sexual characteristics. Not a depletion, a endocrine event
Bone Growth
Female psyche
Fair complexion
Breast Development
Widening of the pelvis
Maturation of genitalia
Female pattern pubic hair
Subcutaneous fat deposition
Ovulation and menstruation
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11
Q

Ovulation

A

Average length of ovulation is 7 days
Increase in FSH concentration
In response to increased FSH, oestrogen concentrations also start to rise

Oestrogens exert negative feedback over FSH, so FSH levels dip and so do oestradiol levels

on about day 12 of the menstrual cycle, get a LH surge, and a little FSH surge (which has no function and may be accidental and accompanies the LH surge)

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12
Q

LH surge during menstrual cycle

A

The signal for the LH surge requires 36 hours of elevated oestradiol, which positively feedbacks the LH
LH causes progesterone secretion plus some oestradiol secretion.

This LH surge is sufficient to generate progesterone and eostradiol for about 7 days, then start to tail off by the end of the month.

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13
Q

What hormone can pop up midcycle in some women?

A

For some women, small amount of testosterones become dominant midcycle because oestradiol and progesterone dip so much.

Results in acne mid-cycle.

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14
Q

FSH and egg maturation

A

FSH causes follicle to mature and as it does, it secretes oestrogens.

During that maturation, the ovum moves to the edge of the follicle and the LH surge causes ovulation. LH surge causes egg to be expelled.

Takes two days for LH to produce its effect. Under influence of LH the remaining cells of the empty follicle turn yellow and secrete loads of progesterone and a bit of oestradiol.

LH is only promoting secretion for 7 days after this secretion falls to 0. second half of cycle is constant, and ovulation occurs 14 days before the first day of the menstrual cycle.

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15
Q

Oestradiol

A

Oestradiol has a thickening effect on the endometrium

When progesterone acts on the endometrium, it causes it to secrete nutrients. When the ovum is ready, it can grow in the endometrium which is warm, thick and nutritious.

Assuming that ovulation does not result in conception, then after 7 days the secretory phase decreases, and the endometrium which has grown because of oestrogen and progesterone, will start to collapse. Any drop in progesterone (regardless of amount) will trigger collapse of the endometrium.

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16
Q

Menstrual bleeding

A

Drop in progesterone causes arteries in endometrium to constrict, so its deprived of blood supply (no oxygen and nutrients) and atrophies (dies).

Tissue becomes anoxic and dies and this causes bleeding. After blood vessels have been constricted for about 18 hours, the blood vessels dilate and the dead tissue around them is washed away by the increased blood supply.

The blood then clots over the endometrium. Over the next few days, the clot undergoes fibrinolysis. Menstrual bleeding is blood which has clotted which is then liquified.

Prostaglandins are produced by the dying cells, which cause uterine contraction and pain.

17
Q

Order of events in menstruation

A

Vasoconstriction, tissue atrophy, vasodilation, washed away, blood clot, fibrinolysis.

18
Q

Cervix during ovulation

A

Cervix prevents bacteria into uterus but has to let sperm through

Oestrogens cause cervix to dilate. It is maximally dilated at the time of ovulation when sperm needs to meet the eggs. Also make the mucus very watery and diluted to allow sperm to swim through (still stops bacteria getting through)

Progesterone closes the cervix - causes it to constrict. Thickens cervical mucous - stops sperm and bacteria getting through

Prostaglandins cause cervix to dilate again later to allow menstrual flow

19
Q

Progesterone effect

A

Progesterone causes an increase in body temperature - day body temperature goes up is the day after ovulation.

Ovulation occurs on day 14.

Ovum has a life expectancy of 38-46 hours, so around day and a half or two days to be fertilised

. Sperm have an active life span of about two days. So in an average menstrual cycle, the fertile window is day 14-16, everything outside that is not fertile.

20
Q

Inhibin in females

A

Inhibin in females goes up at the time of LH surge. It isn’t used in pharmacology but is used in reproductive health. Women with a low inhibin concentration are less likely to respond to assisted reproductive methods.