DHEAS Test
Dehydroepiandrosterone sulfate (DHEAS) is a weak androgen (androgens are hormones that generally stimulate masculine characteristics). DHEAS is normally secreted by the adrenal gland and this test may be used to detect abnormal adrenal function. In women and girls, increased DHEAS causes acne and abnormal hair growth, called hirsutism. This test can be ordered in patients being evaluated for PCOS. Normally, DHEAS levels increase before puberty then decrease significantly with age.
E2 is an estrogen hormone produced by developing follicles in the ovary. E2 testing is used to monitor ovarian function. Ovarian stimulation methods are currently used to stimulate development of multiple follicles, to increase the chances of pregnancy. This therapy can be used for cycles of intrauterine insemination (IUI) or in vitro insemination (IVF). Growth of follicles during ovarian stimulation is usually monitored by ultrasound imaging and with E2 tests. E2 levels increase as follicles grow.
FSH is secreted by the pituitary gland and supports the function of the ovary in the female and the testicles in the male. In mature women, FSH stimulates the growth and development of ovarian follicles during the first part of the menstrual cycle. After premature ovarian failure or menopause there is a decrease in estradiol secretion (see E2 test above). Normally, E2 from the ovarian follicles acts on the pituitary to reduce secretion of FSH (this process is called negative feedback). When E2 levels are low, FSH levels become significantly higher, and these high FSH levels can indicate fewer healthy eggs in the ovary. In men, FSH stimulates normal function of the testicles including production of sperm and testosterone. Testosterone acts on the pituitary gland to decrease FSH secretion. Testicular failure can result in a dramatic increase in FSH levels.
The laboratory blood test for pregnancy detects the level of hCG in blood. Approximately seven days after fertilization, the implanted embryo begins to secrete hCG. The laboratory test for hCG is used to detect when the early pregnancy has been established. During a normal pregnancy, hCG approximately doubles every two days during the first month. The test may be repeated every two days during early pregnancy to determine the health and location of the pregnancy.
Luteinizing hormone (LH) is a hormone secreted by the pituitary gland. In women, LH helps regulate the menstrual cycle and ovulation. LH increases rapidly just before ovulation, called the “LH surge.” LH levels are also useful in the investigation of menstrual irregularities. In men, LH stimulates the production of testosterone by the testicles, which is required for normal sperm production. LH tests can help diagnose pituitary gland disorders or diseases involving the ovaries or testicles. LH can also be used in the diagnosis of precocious (early) or delayed puberty.
After releasing the egg at ovulation, the follicle normally develops into a structure called the corpus luteum (CL). The CL secretes progesterone during the second half of the menstrual cycle. If pregnancy occurs, the CL continues to secrete progesterone, which is important to maintaining the early pregnancy. Serum progesterone tests are used to detect a CL and/or to assess the quality of CL function. Progesterone levels can be used to confirm ovulation, diagnose menstrual cycle abnormalities associated with CL failure, to monitor normal pregnancy (along with hCG and ultrasound), or to monitor CL function during treatment cycles for IUI or IVF.
Prolactin plays an important role in milk secretion during nursing. Normally prolactin secreted by nursing mothers inhibits the ovary so that pregnancy is less likely until the baby is weaned. However, one can not predictably depend on this, so contraception is still recommended if pregnancy is not desired. The prolactin level in non-pregnant women is usually low, but increases somewhat near the time of ovulation during each menstrual cycle. In early pregnancy prolactin levels increase by ten to twenty times, returning to normal after delivery. Abnormally high prolactin in non-pregnant women can inhibit the ovary and cause amenorrhea (lack of menstruation). High prolactin levels also inhibit the testicles in men leading to decreased or absent sperm production and sometimes contributing to erectile dysfunction (ED).
Testosterone is a hormone that is required for male characteristics and fertility, including sperm production and sexual function. It is an androgen, which is the general term for hormones that support male characteristics. Testosterone testing is used to detect low levels in men suffering from infertility, decreased sex drive, and/or erectile dysfunction. In women, much lower amounts of testosterone are secreted by the ovaries and adrenal glands, but these small amounts also contribute to normal sexual function. However, even small increases in testosterone and/or other androgens (see DHEAS test) in women can cause decreased ovarian function and amenorrhea, along with masculinization, including acne and hirsutism (excess male-pattern hair growth). These symptoms and others are often seen with polycystic ovarian syndrome (PCOS). The total testosterone and free-testosterone tests measure the amount of testosterone in the blood, and the amount that is free to act on target organs. The Sex hormone binding globulin (SHBG) test is used to measure what part of the testosterone is bound to proteins in the blood and is not available to act. Situations that can affect the reliability of the results include: women using oral contraceptives, pregnant women and men on testosterone-replacement medication, or treatments that cause androgen production.
Thyroid stimulating hormone (thyrotropin, TSH) is hormone secreted by the pituitary gland, which acts on the thyroid gland. In response, the thyroid gland secretes the thyroid hormones (iodothyronines, T4 and T3). Measurement of TSH in blood has been used as a primary test for the diseases hyperthyroidism (too much thyroid hormone) and hypothyroidism (too little thyroid hormone). Hypothyroidism may be associated with abnormal menstrual cycles, amenorrhea (lack of menstruation), and may affect ovulation and conception. TSH testing is also used to measure how well a patient is responding to thyroid hormone replacement therapy.
The principal thyroid hormone, thyroxine (T4), circulates in blood bound to carrier proteins. The free-T4 is a measure of how much active thyroid hormone is available to the body.
