What are hormones?
The following post is excerpted from information ofund on the Andrology Australia website. I would encourage our readers to visit this excellent site.
Hormones are chemical messengers that are made by glands in the body. Hormones are delivered through the bloodstream and act on other organs in the body. In this section, the role of hormones controlling male reproductive function will be described and includes:
Gonadotropin-releasing hormone (GnRH)
Which is secreted by the hypothalamus that sits at the base of the brain. GnRH controls the secretion of other hormones from the pituitary gland, which is another small gland at the base of the brain. The hypothalamus also has other functions that are not related to reproductive function.
Luteinizing hormone (LH)
Which is secreted by the pituitary gland in response to a GnRH signal. LH acts on the Leydig cells in the testes. Once stimulated with LH, the Leydig cells in the testes produce testosterone.
Follicle stimulating hormone (FSH)
Is also secreted by the pituitary gland in the brain. Together with testosterone, FSH stimulates Sertoli cells (located in the seminiferous tubules of the testes) to support the developing sperm.
Testosterone
Is probably the most familiar ‘male hormone’ produced by LH-stimulated Leydig cells in the testis. Testosterone, together with FSH, is needed for normal sperm production. Of interest, females also produce testosterone but at much lower levels.
Measurement of hormones
Hormones circulate in the blood stream to reach their target organ and are easily measured by taking a blood sample that is sent to a laboratory for testing. Laboratories use ‘reference ranges’ which are hormone levels that are expected for normal healthy people. For 95% of normal healthy people, their hormone levels will fall within this reference range. This also means, however that a few healthy people (5%) will have levels that fall outside the range.
By comparing the blood test result with the reference range, the doctor can tell if there is a lower or higher hormone level than expected. In some situations when low hormone levels are measured, the doctor may suggest that hormone replacement therapy is needed to bring your hormone levels back to normal.
Testosterone is measured by a blood test that is best taken in the morning between 8.00 to 10.00am as this is the time when testosterone is at its peak level. Reference ranges are usually developed on morning blood levels. The normal range for total testosterone levels for healthy young adult men is 8-27 nanomolar (this may vary slightly between different laboratories). Total testosterone is usually measured, which includes both the free testosterone and that attached to the SHBG and albumin carriers.
Hormones are chemical messengers that are made by glands in the body. Hormones are delivered through the bloodstream and act on other organs in the body. In this section, the role of hormones controlling male reproductive function will be described and includes:
Gonadotropin-releasing hormone (GnRH)
Which is secreted by the hypothalamus that sits at the base of the brain. GnRH controls the secretion of other hormones from the pituitary gland, which is another small gland at the base of the brain. The hypothalamus also has other functions that are not related to reproductive function.
Luteinizing hormone (LH)
Which is secreted by the pituitary gland in response to a GnRH signal. LH acts on the Leydig cells in the testes. Once stimulated with LH, the Leydig cells in the testes produce testosterone.
Follicle stimulating hormone (FSH)
Is also secreted by the pituitary gland in the brain. Together with testosterone, FSH stimulates Sertoli cells (located in the seminiferous tubules of the testes) to support the developing sperm.
Testosterone
Is probably the most familiar ‘male hormone’ produced by LH-stimulated Leydig cells in the testis. Testosterone, together with FSH, is needed for normal sperm production. Of interest, females also produce testosterone but at much lower levels.
Measurement of hormones
Hormones circulate in the blood stream to reach their target organ and are easily measured by taking a blood sample that is sent to a laboratory for testing. Laboratories use ‘reference ranges’ which are hormone levels that are expected for normal healthy people. For 95% of normal healthy people, their hormone levels will fall within this reference range. This also means, however that a few healthy people (5%) will have levels that fall outside the range.
By comparing the blood test result with the reference range, the doctor can tell if there is a lower or higher hormone level than expected. In some situations when low hormone levels are measured, the doctor may suggest that hormone replacement therapy is needed to bring your hormone levels back to normal.
Testosterone is measured by a blood test that is best taken in the morning between 8.00 to 10.00am as this is the time when testosterone is at its peak level. Reference ranges are usually developed on morning blood levels. The normal range for total testosterone levels for healthy young adult men is 8-27 nanomolar (this may vary slightly between different laboratories). Total testosterone is usually measured, which includes both the free testosterone and that attached to the SHBG and albumin carriers.
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