Introduction
Follicle-stimulating hormone (FSH) is essential for sexual development and reproduction in men and women. It is vital for the normal functioning of the ovaries and testes. FSH is present before pregnancy, and it is one of the hormones that are essential for conception. FSH plays a vital role in supporting pregnancy by exerting various physiological functions. In addition, ideal levels of FSH are essential during pregnancy.
What Is Follicle-Stimulating Hormone (FSH)?
The pituitary gland in the brain produces a hormone called follicle-stimulating hormone (FSH). It is made in the anterior pituitary in response to stimulation by the gonadotropin-releasing hormone from the brain's hypothalamus. FSH affects the functioning of the testis and ovaries and plays a vital role in sexual development. It is essential for estrogen production and follicular development in females and the induction and maintenance of spermatogenesis in males.
What Are the Functions of Follicle-Stimulating Hormone?
Follicle-stimulating hormone exerts various functions depending on the individual's age and the type of sexual organ. It involves the following functions:
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Role of FSH in Fetal Development:
The fetal pituitary gland releases FSH and LH (luteinizing hormone) hormones during pregnancy's second and third trimesters. These hormones help mature the fetus's ovarian follicles or seminiferous tubules during mid-pregnancy.
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Role of FSH in Puberty:
FSH levels are usually low in children. The gonadotropin-releasing hormone produced by the hypothalamus stimulates the production of FSH and LH when puberty approaches, which is between ages 10 and 14. This hike in FSH production initiates changes in sexual development and maturity. In males, FSH works with LH and stimulates the testes to produce testosterone. The testosterone hormone is responsible for physical changes during puberty. In girls, FSH and LH hormones trigger the ovaries to produce estrogen, which is responsible for material changes such as menstruation and the development of breasts.
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Role of FSH in Menstruating Females:
FSH hormone is essential for regulating the menstrual cycle. It helps stimulate the growth of ovarian follicles in menstruating women and helps in ovulation. FSH plays a role in preparing the eggs for ovulation. It causes the follicles in the ovaries to mature. On the fourteenth day of menstruation, LH surge causes the rupture of mature follicles and the release of the egg. The ruptured follicle becomes a temporary endocrine gland after ovulation and produces high progesterone levels, which prepares the uterine lining for pregnancy. If fertilization does not occur, the corpus luteum breaks down, and the progesterone level decreases. Further, the menstrual cycle begins, and FSH begins to rise.
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Role of FSH in Males:
FSH plays a role in sperm production in males. Though LH triggers the testosterone inside the testes for sperm production, FSH also helps in sperm production.
What Is the Role of FSH in Pregnancy?
Though FSH levels decrease during pregnancy, studies have shown that the continued function of FSH is required for a successful pregnancy. Studies have shown that FSH exerts functional roles in the placenta and the uterine myometrium during pregnancy. Studies performed in the reproductive tissues of pregnant women showed that FSH was observed in the arterial smooth muscles and vascular endothelium. In addition, it is also present in the placenta in the stroma, umbilical cord, amnion, decidua, and myometrium.
FSH, present in the placental vascular endothelium, promotes angiogenesis (blood vessel formation) in the fetal vessels. The normal development and functioning of the placenta are essential for a healthy pregnancy. Impairments in the development of the placenta may cause growth retardation in the fetus, placental insufficiency, and fetal death. The maternal-fetal exchange of nutrients and oxygen through the placenta requires extensive angiogenesis. In addition, abnormalities in placental angiogenesis are responsible for various pregnancy complications. Therefore, FSH is essential for the angiogenesis of the placental vessels and for a successful pregnancy outcome.
FSH in the myometrium (outer muscular layer of the uterus) regulates uterine contractions. FSH is expressed in the myometrium of the uterus in pregnant and nonpregnant women. However, FSH levels are upregulated in pregnant women, and the upregulated levels in the myometrium mediate contractile activity. However, the reason for a decrease in the ranks of FSH during the early and mid-pregnancy period to facilitate implantation and the maintenance of pregnancy and the uterine contractility promoted by the upregulated FSH levels during parturition is yet to be determined.
FSH also plays a vital role in increasing estrogen production in the ovaries. Estrogen is essential for preparing the uterine myometrium to receive the embryo. FSH ramps the estrogen supply to successfully implant the embryo (fertilized egg).
What Is the Normal FSH Level During Pregnancy?
In menstruating women, FSH levels should be between 4.7 and 21.2 mIU/ml. In general, FSH levels are usually too low to be measured during pregnancy. Ideal FSH levels are essential during pregnancy because it helps in placenta formation. FSH is crucial during the initial months of pregnancy. During pregnancy, the FSH levels should be ideally below two milli-international units per milliliter (mIU/ml). As the pregnancy progresses, the FSH levels should be between three to ten milli-international units per milliliter. FSH levels remain low during pregnancy and return to normal after delivery during the follicular phase of the menstrual cycle. An increase in FSH levels is associated with miscarriage or unexplained recurrent pregnancy loss. Also, the conception rate is reduced in women with FSH levels greater than 15 mIU/ml.
How Are FSH Levels Measured?
A blood test helps determine FSH levels. FSH blood tests are performed to determine the cause of infertility, the cause of the dysfunction of the ovaries or testis, and diagnose pituitary or hypothalamus conditions. It can also help determine menstrual irregularities and analyze the reason for delayed or early puberty.
Conclusion
Follicle-stimulating hormone (FSH) exerts physiologic effects essential for sexual development and fertility. FSH is generally not required after conception as ovulation is unnecessary. However, the pituitary gland secretes small amounts of FSH even during pregnancy as it exerts various physiological effects essential for a successful pregnancy. In addition, an FSH test is suggested during pregnancy to screen for certain conditions.
