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Reproductive Hormones

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Reproductive Hormones

Female Reproductive Hormones

FSH and LH stimulate the ovaries to produce mature gametes, as well as to synthesize and secrete oestrogen, the main female reproductive hormone. Women have two ovaries on either side of the uterus. The tubes that connect the ovaries to the uterus are called fallopian tubes or uterine tubes.

Menstrual cycle reproductive hormones functions

The levels of LH, FSH, oestrogen and progesterone in the bloodstream go through a cycle every month called the menstrual cycle. The first menstrual period happens between the ages of 11 and 15 and continues to recur every month until the beginning of menopause between the ages of 45 and 55. Each cycle normally lasts an average of 28 days (21-35 days).

The menstrual cycle refers to a monthly cycle of natural changes that occur in the female reproductive system. These changes are necessary for the production of an egg cell every month, as well as for preparing the uterus for pregnancy.

The menstrual cycle is controlled by feedback systems:

Moderate levels of oestrogen have a negative feedback effect on the HPG axis, lowering the amounts of LH and FSH released to return the oestrogen back to baseline levels. High levels of oestrogen in the presence of progesterone also have negative feedback on the HPG axis. However, high oestrogen levels without progesterone exert a positive feedback effect on the HPG axis, causing more LH and FSH to be released.

A positive feedback system, unlike negative feedback systems, amplify stimuli instead of reversing homeostatic disturbances!

The events that transpire during the menstrual cycle can be described in the context of two separate cycles, the ovarian and the uterine cycles.

The ovarian cycle

The ovarian cycle consists of two phases. The follicular phase, and the luteal phase. Ovulation occurs between these two phases. It marks the end of the follicular phase and the start of the luteal phase. The follicular phase marks the beginning of a new cycle as follicles begin to mature and prepare to release an oocyte.

An ovarian follicle is a group of cells found in the ovaries that surround an egg cell and secrete hormones that regulate the menstrual cycle. Women have roughly 200,000 to 300,000 follicles at the time of puberty, each with the capacity to produce a mature egg cell for fertilization upon ovulation, meaning the release of an egg from the ovaries.

The oocyte is another term for a mature egg cell that is released every month from the ovaries.

There is minimal FSH, LH, and oestrogen in the blood at the start of a new cycle, so many follicles begin to grow independently of these hormones. Because oestrogen levels are low, there is little negative feedback acting on the HPG axis, leading to an increase in FSH and LH levels. These increase the follicle's growth and the production of oestrogen. During each menstrual cycle, only one dominant follicle can continue to grow and be released. As oestrogen levels rise to moderate levels, negative feedback decreases FSH levels, allowing just the dominant follicle to survive, which is now capable to grow independently of FSH. Follicular oestrogen gradually rises and because there is minimal progesterone in the system at this time, it exerts positive feedback on the HPG axis, triggering an upsurge in LH levels. The follicle releases the mature oocyte into the fallopian tube in response to the LH surge. This process is called ovulation. For around 24 hours, the oocyte remains viable for fertilization.

Following ovulation in the luteal phase, the remnant of the ruptured follicle becomes the corpus luteum and continues to secrete oestrogen and, for the first time, progesterone. Oestrogen in presence of progesterone exerts negative feedback on the HPG axis which lowers the LH and FSH levels to prevent the formation of any new follicles in the ovaries. Oestrogen and progesterone also maintain suitable conditions for fertilisation of the oocyte and implantation.

  • In the absence of fertilisation, the corpus luteum spontaneously regresses after 14 days at the end of the cycle. This causes a considerable drop in hormone levels which removes the negative feedback on the HPG axis and allows it to reset and prepare for a new cycle to begin anew.
  • If fertilisation happens, the embryo's placenta generates a hormone called the human chorionic gonadotropin (hCG), which keeps the corpus luteum intact. After a while, however, the placenta starts making oestrogen and progesterone itself and the corpus luteum eventually regresses.

The uterine cycle

The uterine cycle describes the events that occur inside the uterus during the menstrual cycle, and it consists of three phases: menstruation, the proliferative phase, and the secretory phase.

  • Menstruation signifies the start of a new menstrual cycle. It happens without fertilization after the corpus luteum has regressed, and the uterine lining has started to shed. Menstrual bleeding normally lasts 2-7 days, with the average woman losing between 10-80ml of blood.
  • Following menstruation, the proliferative phase occurs concurrently with the follicular phase of the ovary, preparing the reproductive tract for fertilization and implantation. Oestrogen causes the uterine lining to thicken, as well as the secretion of a thin alkaline cervical mucus that aids sperms' entrance into the uterus.
  • The secretory phase occurs along with the luteal phase. Progesterone promotes the thickening of the uterine lining as well as the development of secretory glands. In the presence of oestrogen, progesterone induces the cervix to generate a thick acidic mucus that inhibits any further sperms from entering. These two hormones also stimulate breast tissue growth and other metabolic changes that slightly raise the average body temperature.

Check out the Menstrual Cycle Hormones article to learn more!

Menstrual cycle hormone graph

The female reproductive hormone cycles outlined above are summarized in the graph below.

Therapeutic Reproductive Hormones Functions

Exogenous hormones can be used in certain scenarios for therapeutic purposes, like Hormone replacement therapy (HRT) or Transgender hormone therapy (THT).

Hormone Replacement Therapy

Hormone replacement therapy (HRT) is an effective treatment for the symptoms of menopause. HRT can also help with other long-term health issues connected with menopause, including lowering the risk of osteoporosis, cardiovascular disease, and stroke. The goal of HRT is to supplement the reduced hormone levels caused by menopause.

When the ovaries cease producing eggs, menopause has started. The hormones oestrogen and progesterone are lowered in the blood as a result of menopause. In addition to subfertility, menopause can cause symptoms such as hot flushes, dryness of the vagina and weakening of the bones. HRT works by replenishing these hormones to some degree to lower menopausal symptoms and health concerns.

Transgender Hormone Therapy

Transgender hormone therapy (THT) is a type of hormone therapy in which sex hormones and other pharmacological drugs are given to transgender people to match their secondary sexual traits more closely with the gender they identify themselves with. This sort of hormone therapy is classified into two groups based on whether the target of the treatment is masculinization or feminization:

  1. In the form of masculinizing hormone therapy, transgender males or transmasculine persons are administered testosterone and anti-oestrogen drugs.
  2. In contrast, feminizing hormone treatment involves the administration of oestrogen and anti-testosterone medications to transgender women or transfeminine persons.

Reproductive Hormones - Key Takeaways

  • Reproductive hormones, also known as sex hormones, are steroids hormones that play important roles in the development and maintenance of sexual characteristics, fertility, pregnancy, and menstruation.
  • The hypothalamus secretes gonadotrophin-releasing hormone (GnRH) which acts on the anterior pituitary and stimulates it to produce and release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
  • Testosterone is the main male sex hormone and Oestrogen is the main female sex hormone.
  • The ovarian cycle consists of two phases: the follicular phase and the luteal phase. The uterine cycle describes the events that occur inside the uterus during the menstrual cycle, and it consists of three different phases.

Frequently Asked Questions about Reproductive Hormones

Reproductive hormones, also known as sex hormones, are steroids hormones that play important roles in the development and maintenance of sexual characteristics, fertility, pregnancy, and menstruation.  


Moderate levels of oestrogen have a negative feedback effect on the HPG axis, lowering the amounts of LH and FSH released in order to return the oestrogen back to baseline levels. High levels of oestrogen in the presence of progesterone also have negative feedback on the HPG axis.

However, high oestrogen levels in the absence of progesterone exert a positive feedback effect on the HPG axis, causing more LH and FSH to be released.

Oestrogen is the main female reproductive hormone.


Testosterone is the main male reproductive hormone.

Menstruation, follicular phase, ovulation, and luteal phase

LH, and FSH from the anterior pituitary. Oestrogen and progesterone from the ovaries. 

FSH and LH stimulate the ovaries to produce mature gametes, as well as to synthesize and secrete oestrogen. High levels of oestrogen exerts positive feedback on the HPG axis causing a surge in LH levels which results in ovulation. Oestrogen also promotes growth of breast tissue and makes the uterine environment suitable for fertilization. Progesterone is released after ovulation, the luteal phase. To prevent polyspermy, progesterone make the cervical environment less suitable for sperms to enter. 

The menstrual cycle is controlled by feedback systems:

Moderate levels of oestrogen have a negative feedback effect on the HPG axis, lowering the amounts of LH and FSH released to return the oestrogen back to baseline levels. High levels of oestrogen in the presence of progesterone also have negative feedback on the HPG axis. However, high oestrogen levels without progesterone exert a positive feedback effect on the HPG axis, causing more LH and FSH to be released.

There is minimal FSH, LH, and oestrogen in the blood at the start of a new cycle. Because oestrogen levels are low, there is little negative feedback acting on the HPG axis, leading to a gradual increase in FSH and LH levels. These increase the follicle's growth and the production of oestrogen. Follicular oestrogen gradually rises when it reaches high levels, it exerts positive feedback on the HPG axis, triggering an upsurge in LH levels and leading to ovulation. After ovulation, the remnant of the primary follicle, now called the corpus luteum, releases both oestrogen and progesterone.

Final Reproductive Hormones Quiz

Question

What gland secretes gonadotrophin-releasing hormone (GnRH)?

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Answer

The hypothalamus

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Question

What hormones are released from the anterior pituitary in response to GnRH?

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Answer

LH and FSH

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Question

What is the role of LH in the male body?

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Answer

LH stimulates special cells in the testes to produce testosterone, the main male sex steroid hormone. 

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What does testosterone do?

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Answer

Testosterone has numerous roles in the body. It stimulates spermatogenesis in the testes and is essential for maintaning libido. Other actions of testosterone include development of secondary sexual characteristics through puberty (e.g. pubic and facial hair), growth of external genitalia, as well as deepening of the voice. 

Testosterone also has anabolic effects and stimulates the growth of bone and muscle. 

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Question

What is the role of FSH in the male body?

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Answer

FSH targets another series of special cells in the testes and drives spermatogenesis in the testes. 

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Question

what is the menstrual cycle?

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Answer

The menstrual cycle refers to a monthly cycle of natural changes that occur in the female reproductive system. These changes are necessary for the production of an egg cell every month as well as for preparing the uterus for pregnancy. 

Show question

Question

when does the menstrual cycle first start?

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Answer

The first menstrual period happens between the ages of 11 and 15 

Show question

Question

what phases are in the ovarian cycle?

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Answer

The ovarian cycle consists of two phases. The follicular phase, and the luteal phase. 

Show question

Question

what is an ovarian follicle?

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Answer

An ovarian follicle is a group of cells found in the ovaries that surround an egg cell and secrete hormones that regulate the menstrual cycle. Women have roughly 200,000 to 300,000 follicles at the time of puberty, each with the capacity to produce a mature egg cell for fertilisation upon ovulation.

Show question

Question

what is corpus luteum and what does it do?

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Answer

The remnant of the ruptured follicle becomes the corpus luteum and continues to secrete oestrogen and, for the first time, progesterone 

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Question

what happens to the corpus luteum in the absence of fertilisation?

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Answer

In the absence of fertilisation, the corpus luteum spontaneously regresses after 14 days at the end of the cycle. 

Show question

Question

what happens to the corpus luteum when fertilisation occurs?

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Answer

If fertilisation happens, the embryo's placenta generates a hormone called the human chorionic gonadotropin (hCG), which keeps the corpus luteum intact. After a while, however, the placenta starts making oestrogen and progesterone itself and the corpus luteum eventually regresses. 

Show question

Question

What phases are in the uterine cycle?

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Answer

it consists of three phases: menstruation, the proliferative phase, and the secretory phase.  

Show question

Question

what is hormone replacement therapy?

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Answer

Hormone replacement therapy (HRT) is an effective treatment for the symptoms of menopause. HRT can also help with other long-term health issues connected with menopause, including lowering the risk of osteoporosis, cardiovascular disease, and stroke. The goal of HRT is to supplement the reduced hormone levels caused by menopause.

Show question

Question

what drugs are used in masculinising hormone therapy?

Show answer

Answer

In masculinising hormone therapy, transgender males or transmasculine persons are administered testosterone and anti-oestrogen drugs.

Show question

Question

what drugs are used in feminising hormone therapy?


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Answer

Feminising hormone treatment involves the administration of oestrogen and anti-testosterone medications to transgender women or transfeminine persons.

Show question

Question

What feedback loop amplifies responses?

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Answer

Positive Feedback

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Question

What characterises negative feedback loops?

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Answer

Negative feedback loops are characterised by the return of basal levels when there has been a deviation.

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Question

What ion is responsible for the release of glucagon and insulin?

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Answer

Calcium

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What characterises a positive feedback loop?

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Answer

Positive feedback loops are characterised by the amplification of a change in a system.

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Question

What type of feedback loop is used in blood glucose regulation?

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Answer

Negative.


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What type of feedback loop is used in temperature regulation? 

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Answer

Negative.

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What type of feedback loop is used in blood pressure regulation?

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Negative.

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What type of feedback loop is used in osmolarity regulation?


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Negative.

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What type of feedback loop is often used in hormonal control?


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Negative.


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What type of feedback loop is used in the creation of nerve impulses?

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Positive.

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What type of feedback loop is used in ovulation?


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Positive.

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What type of feedback loop is used in birth?

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Positive.

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What type of feedback loop is used in blood clotting?


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Positive.


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Question

What are the key components of a negative feedback loop?

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Answer

  • Stimulus
  • Sensor
  • Controller
  • Effector

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What does an effector do in a feedback loop?

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Effectors carry out the response. For example, effectors include sweat glands and skeletal muscles.

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What is a stimulus in feedback loops?

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The stimulus is the change in an environment that triggers a response.

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What is the sensor in a feedback loop?

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The sensor detects the stimulus.

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What is the controller in a feedback loop?

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The controller analyses the variance in the stimulus, from signals provided by the sensors. Once the variance from the baseline value exceeds a given threshold, it activates the effector. 

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Question

What reflex controls blood pressure?

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Answer

The baroreceptor reflex.

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Question

What is infertility? 

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Answer

infertility can be defined as the inability to get pregnant after a year or more of regular unprotected intercourse. 

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what are the types of infertility?

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Answer

There are two types of infertility: primary and secondary. 

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Question

What factors can lead to infertility in men?

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Answer

Kilenfelter syndrome (XXY) , sterilisation and erectile dysfunction  

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What factors can lead to infertility in women? 

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Answer

Ovulatory disorder, Fallopian tube damage, and Disorders of the uterus 


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What is PCOS? 

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Answer

Polycystic ovarian syndrome (PCOS) is a disorder in which the ovaries generate an abnormally large quantity of androgens, male sex hormones, or eostrogen that disturb the HPG axis and result in irregular and infrequent ovulation.  

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What is fertility treatmen?

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Fertility treatment refers to any type of therapy or medical procedure that increases a couple's chances of successfully conceiving a child and becoming pregnant. 

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What are the types of fertility treatment?

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Answer

Fertility treatments can be categorized into three main types: Hormone therapy, surgical procedures, and assisted conception.  

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Question

How hormones can be used to improve fertility?

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Answer

Extrinsic hormones or anti hormone drugs can be used to treat infertility, especially when the female is not generating enough eggs. This is often due to the anterior pituatry not secreting enough follicle stimulating hormone (FSH) and leutenising hormone (LH) to promote egg maturation and release.  

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What issue should be considered with regards to hormones to treat infertility? 

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Answer

several eggs can be released at the same time which would increase the likelihood of having twins or triplets. 

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How can surgical procedures be used to improve fertility in women?

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Answer

In women, major surgical procedures that are used to improve fertility include the surgical opening of blocked or scarred fallopian tubes to allow eggs to be released, and surgical removal of ovarian cysts in PCOS.  

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How can surgical procedures be used to improve fertility in men? 

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Answer

Surgical procedures in some cases can be used to improve fertility in men as well. Surgical extraction of sperm is a viable option for those who have obstruction preventing the release of sperm or those who would like to reverse their vasectomy.  

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What is assisted conception and what are the two main methods it includes?

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Answer

The use of medical interventions other than hormone medicines or surgery alone to help couples concieve and have a child is known as assisted conception. Artificial insemination and in vitro fertilisation (IVF) are two of these methods.


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What is artificial insemination?

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Answer

a procedure that involves delivering sperms into the uterus via a tiny plastic tube that is inserted through the vagina and the cervix. For this procedure, sperms are collected and only the top quality and the quickest ones are chosen. 


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What is IVF?

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Answer

IVF is the process of fertilising an egg outside of the body ('in vitro' means 'in glass'). 

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Question

Why does the mother need to receive FSH and LH injections for IVF?

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Answer

for the purpose of stimulating her ovaries to produce more eggs than normal so they can be extracted from the ovaries 

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