Systems Biology
Hormonal control of reproduction involves key endocrine structures such as the hypothalamus, the pituitary gland, and the gonads (testes in males, ovaries in females). At the beginning of puberty, the hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH control reproduction and sexual development in both males and females, but their specific functions differ depending on sex.
In males, FSH acts on Sertoli cells facilitating spermatogenesis, while LH causes Leydig cells to synthesize and release the primary male sex hormone, testosterone. Testosterone is essential for the development of secondary sex characteristics and the production of mature sperm. In females, FSH causes the ovaries to release estrogens, responsible for the development of secondary sex characteristics and the growth and maintenance of the reproductive system, including the endometrium. LH, on the other hand, causes the corpus luteum to release the sex hormone progesterone, which is needed for the development and maintenance of the endometrium.
Lesson Outline
<li>Important endocrine structures: hypothalamus, pituitary gland, and gonads</li> </ul><br> <li>Reproductive events in both sexes</li> <ul> <li>Gonadotropin-releasing hormone (GnRH) released by the hypothalamus at puberty</li> <li>GnRH stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland</li> <li>FSH and LH act on the gonads (testes and ovaries)</li> </ul> <li>Male sexual development</li> <ul> <li>FSH acts on Sertoli cells in seminiferous tubules to facilitate sperm maturation</li> <li>LH acts on Leydig cells in testes to produce and release testosterone</li> <li>Functions of testosterone in males:</li> <ul> <li>Development of secondary sex characteristics (e.g., facial hair, deepening voice, increased muscle mass)</li> <li>Support spermatogenesis (along with FSH)</li> </ul> </ul> <li>Female sexual development</li> <ul> <li>FSH acts on ovaries to stimulate release of estrogens</li> <li>Functions of estrogens in females:</li> <ul> <li>Development of secondary sex characteristics (e.g., breast growth, widening hips)</li> <li>Growth and maintenance of the reproductive system (including thickening of the endometrium)</li> </ul> <li>LH acts on the corpus luteum in the ovaries to stimulate synthesis and release of progesterone</li> <ul> <li>Role of progesterone:</li> <ul> <li>Maintenance of the endometrium</li> </ul> </ul>
Don't stop here!
Get access to 71 more Systems Biology lessons & 8 more full MCAT courses with one subscription!
FAQs
The hypothalamus produces and releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH then regulate the development, growth, and function of the gonads (ovaries and testes) in both males and females, influencing the production of sex hormones such as estrogens, testosterone, and progesterone.
In females, FSH stimulates the growth and development of ovarian follicles, which contain eggs. It also regulates estrogen production by the follicle cells. LH triggers ovulation, the release of an egg from the ovary, and promotes the formation of the corpus luteum, a remnant of the follicle that secretes progesterone. In males, FSH supports the production of sperm cells within the testes; LH stimulates the production of testosterone, which helps maintain sperm production and is responsible for male sexual characteristics.
In females, estrogens (mainly estradiol) induce the development of secondary sexual characteristics such as breast growth, fat distribution, and menstrual cycles. They also regulate the maturation of eggs in the ovaries. Testosterone is the primary male sex hormone and is responsible for the development of secondary sexual characteristics such as facial hair, deepening of the voice, and increased muscle mass. It also plays a role in sperm production. Progesterone, mainly found in females, plays a crucial role in regulating the menstrual cycle and maintaining pregnancy by preparing the uterus for implantation and the development of the fetus.
Dysfunction in the hormonal control of reproduction can lead to various reproductive disorders and health issues. In females, hormonal imbalances can cause menstrual cycle irregularities, polycystic ovary syndrome (PCOS), infertility, and early menopause. In males, hormonal dysfunction may lead to delayed or early puberty, infertility due to low sperm production, and hypogonadism, which is a condition where the testes do not function properly. Sometimes, hormonal dysfunction may also result from or contribute to the development of tumors in the hypothalamus or pituitary gland. Treatment options for hormonal imbalances may include hormone therapy, medications, or lifestyle changes such as diet and exercise.
