What are sexual hormones? 

Sex hormones are hormones that play a crucial role in the development and functioning of the reproductive system. They are responsible for the development of secondary sexual characteristics, regulation of the menstrual cycle, and maintenance of reproductive tissues in both males and females. 

Hormonal control of the menstrual cycle:

The menstrual cycle is a complex, regulated process involving the interplay of hormones to prepare the female body for potential pregnancy. The key hormones involved in this process are Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), estrogen, and progesterone.

Follicle-Stimulating Hormone (FSH):

Follicle-Stimulating Hormone (FSH) plays a crucial role in the menstrual cycle by initiating and promoting the growth of ovarian follicles. During the early part of the cycle, FSH stimulates several follicles in the ovaries to develop. Each follicle contains an immature egg. As these follicles mature, they produce increasing amounts of estrogen. FSH’s primary function is to support the development of these follicles, ensuring that one becomes dominant and capable of releasing a mature egg during ovulation.

Luteinizing Hormone (LH):

Luteinizing Hormone (LH) takes center stage during the midpoint of the menstrual cycle, triggering the process of ovulation. As estrogen levels peak, the high concentration of estrogen signals the pituitary gland to release a surge of LH. This surge is responsible for the final maturation of the dominant follicle and the subsequent release of a mature egg from the ovary. The release of LH marks the midpoint of the menstrual cycle and is a crucial event in the preparation for potential fertilization.

Estrogen:

Estrogen, primarily produced by the developing follicles in the ovaries, is a key player in the menstrual cycle. During the follicular phase, rising estrogen levels stimulate the growth and thickening of the uterine lining (endometrium). This prepares the uterus for the potential implantation of a fertilized egg. Additionally, a surge in estrogen just before ovulation contributes to the release of LH, which triggers the release of the mature egg from the follicle. Estrogen’s influence extends beyond the reproductive system, contributing to the development of secondary sexual characteristics and overall hormonal balance.

Progesterone:

After ovulation, the ruptured follicle transforms into a structure called the corpus luteum, which is responsible for producing progesterone. Progesterone is essential for maintaining the uterine lining during the luteal phase of the menstrual cycle. If fertilization occurs, the embryo relies on progesterone to sustain a supportive environment for implantation and early pregnancy. However, if fertilization does not occur, the corpus luteum regresses, leading to a decline in progesterone levels. This drop in progesterone signals the uterus to shed its lining, initiating menstruation and marking the start of a new menstrual cycle.

In the menstrual cycle, hormones like FSH help eggs in the ovaries grow, like helpers getting things ready. LH gives a signal for a mature egg to come out, a bit like a special moment for the egg. Estrogen makes a cozy home in the girl’s belly, preparing the uterus for a potential baby. Lastly, progesterone helps maintain that cozy home, but if there’s no baby, it cleans up and gets ready for the next chance. These hormones work together in two phases: FSH and LH help eggs grow and come out in the first part, and estrogen and progesterone maintain the uterus and prepare for a baby in the second part. If there’s no baby, the cycle starts again with the shedding of the uterine lining, like having a little monthly party in the belly.

Hormones in Fertility and Contraception Teatment:

Reasons of infertility: 

In males: 

• Male infertility can result from issues with sperm production, such as low sperm count or poor sperm motility, reducing the chances of fertilization.
• Structural abnormalities, such as blocked sperm ducts or enlarged veins in the testes , can impede the release or transport of sperm.
• Hormonal imbalances, genetic factors, vasectomy, infections, environmental toxins, and lifestyle factors like smoking or excessive alcohol consumption can also contribute to male infertility.

In Females: 

• Female infertility can result from ovulatory disorders, where irregular or absent ovulation disrupts the release of eggs necessary for fertilization.

• Structural issues like blocked fallopian tubes, uterine abnormalities, or outgrowth of uterine lining  can hinder the transport of eggs or implantation of embryos.

• Hormonal imbalances, age-related decline in egg count, pelvic inflammatory disease, autoimmune conditions, and lifestyle factors such as stress or excessive exercise can also impact female fertility.

Fertility Drugs: 

Stimulation of Ovulation:

• Fertility drugs stimulate the release of hormones from the pituitary gland that regulate ovulation.
• These medications induce the development and release of mature eggs from the ovaries, increasing the chances of conception.

Regulation and Enhancement of Follicle Growth:

• Some fertility drugs help correct hormonal imbalances that may disrupt the menstrual cycle and ovulation.
• Gonadotropins, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH), can be administered to stimulate follicle growth in the ovaries.
• By promoting the development of multiple follicles, fertility drugs increase the likelihood of successful ovulation and fertilization.

Monitoring and Adjusting Treatment:

• Fertility specialists closely monitor the response to fertility drugs through ultrasound scans and hormone level measurements.
• Dosages may be adjusted based on individual patient responses to optimize treatment outcomes while minimizing the risk of side effects.

Potential Side Effects and Risks:

• Multiple pregnancies (e.g., twins or triplets), 
• Ovarian hyperstimulation syndrome (ovarian enlargement and fluid accumulation in the abdomen and chest cavity). 
• Mood swings.
• Require close monitoring from healthcare experts.

Artificial insemination and in vitro fertilization (IVF) in captive breeding programmes: 

Artificial Insemination:

• Artificial insemination is a process where sperm is collected from a male and introduced into the female reproductive tract at the appropriate time for fertilization.
• This technique is used to overcome issues related to breeding incompatibility or behavioral problems that prevent natural mating.
• Artificial Insemination allows for the efficient use of genetic material from valuable or difficult-to-breed individuals.

In Vitro Fertilization (IVF):

• In vitro fertilization involves the fertilization of an egg by a sperm in a laboratory setting, outside the body of the female.
• The fertilized egg (zygote) is then transferred into the reproductive tract of a surrogate mother or the original female for development and birth.
• IVF is useful when natural fertilization is challenging or when there is a risk of disease transmission or genetic complications. 
• It allows for the production of offspring from individuals that may be infertile or have reproductive issues.
• Fertility drugs are often used in conjunction with assisted reproductive technologies such as in vitro fertilization (IVF) or intrauterine insemination (IUI).
• Fertility drugs optimize the timing of ovulation and maximize the number of mature eggs available for fertilization during ART procedures.

These assisted reproductive technologies (ARTs) are employed in captive breeding programs for endangered species to:

• Overcome reproductive barriers and increase the chances of successful breeding.
• Introduce new genetic diversity from wild or geographically separated populations.
• Manage and maintain genetic diversity in small or fragmented captive populations.
• Establish genome resource banks for future breeding efforts through cryopreservation (freezing) of embryos.