AssessmentsEstrogen and progesterone
Estrogen and progesterone
is a female hormone that has a mild thermogenic action, increasing basal body temperature during the luteal phase of the menstrual cycle.
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 20-year-old female presents to the clinic with the complaints of irregular menstrual bleeding and breast tenderness. History reveals two months ago she was placed on medroxyprogesterone acetate injections for contraception. A urine pregnancy test at that time was negative. She is sexually active with one partner and does not use condoms during intercourse. The patient's symptoms are most likely due to which of the following?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Sam Gillespie, BSc
Estrogen and progesterone are the female sex hormones, and they’re produced mainly by the ovaries - the female gonads.
The female body can synthesize 3 types of estrogens: estradiol, estrone and estriol.
Of the three, the ovaries synthesize estradiol, which is the most biologically active of them all, and accounts for the majority of sex-specific changes that begin in puberty - like monthly ovulation and menstruation as well as the development of the secondary sex characteristics.
Small amounts of estrogen are also produced by the adrenal cortex and fat cells in adipose tissue, and the placenta secretes these hormones during pregnancy, as well.
But during the reproductive period, it’s the ovaries that produce the majority of estrogen and progesterone in the female body.
Before puberty, the hypothalamus secretes small amounts of a hormone called gonadotropin-releasing hormone, or GnRH.
That GnRH travels to the nearby pituitary, which secretes two hormones of its own - follicle stimulating hormone, or FSH, and luteinizing hormone, or LH.
Once puberty hits, the hypothalamus starts to secrete GnRH in pulses, sometimes more and sometimes less, and FSH and LH make the ovarian follicles develop and secrete hormones.
The ovarian follicles are scattered throughout the ovaries, and each ovarian follicle is made up of a ring of follicular cells surrounding a primary oocyte at its core.
How much of these hormones is secreted is directly related to the phases of the female menstrual cycle.
The variations in FSH and LH levels result in fluctuating levels of estrogen and progesterone that vary according to the phases of the menstrual cycle - the two weeks before ovulation are called the follicular phase, during which mostly estrogen is produced.
Right before ovulation, the really high estrogen levels make the pituitary much more sensitive to the actions of hypothalamic GnRH, and so, they turn into a positive feedback signal, leading to a massive surge of FSH and LH that leads to ovulation.
In turn, the levels of progesterone decrease as well, and menstruation follows.
Another enzyme in theca cells called 3-beta-hydroxysteroid dehydrogenase converts some of the pregnenolone into progesterone.
However, most of the pregnenolone is converted to 17-hydroxypregnenolone, and then into dehydroepiandrosterone, or DHEA.
3-beta-hydroxysteroid dehydrogenase, is quite the over achieving enzyme because it also acts on DHEA and converts it into androstenedione - a testosterone precursor.
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