*10.1.3 Control of gonadotropin secretion*

LH and FSH secretion is under the influence of gonadotropin-releasing hormone (GnRH, also known as LH-releasing hormone). GnRH is a ten amino acid peptide that is synthesized and secreted from hypothalamic neurons and binds to receptors on gonadotrophs.

As depicted in **Figure 1** below, GnRH stimulates secretion of LH, which in turn stimulates gonadal secretion of the sex steroids testosterone, estrogen and progesterone. In a classical negative feedback loop sex steroids(oestrogens, progesterone, testosterone) inhibit secretion of GnRH and also appear to have direct negative effects on gonadotrophs.

This regulatory loop leads to pulsatile secretion of LH and, to a much lesser extent, FSH. The number of pulses of GnRH and LH varies from a few per day to one or more per hour. In females, pulse frequency is clearly related to stage of the cycle.

Several hormonal substances such as inhibin and activin from the gonads, which selectively inhibit and activate FSH secretion from the pituitary, influence GnRH secretion, and positive and negative control over GnRH [69]. Thus gonadotropin secretion is actually considerably more complex than depicted in **Figure 1** below.

**199**

*Metabolic Syndrome in Reproductive Health: Urgent Call for Screening*

**10.2 Metabolic syndrome and impact on reproductive health**

Obesity is a cardinal feature of MetSy and has been increasing in [70]. The effect of obesity on reproduction and as a cause of female infertility has been more extensively studied in females [70]. Obesity has been recently associated with an increased incidence of male factor infertility. A study from Norway looked at planned pregnancies and the time to achieving pregnancy, after adjusting for female BMI and smoking habits, the results showed that overweight and obese men had an odds ratio of infertility of 1.19 and 1.36, respectively [71]. Ramlau-hansen et al. [72] conducted a similar study comprising nearly 48,000 couples for six years assessing the effects of both male and female obesity on infertility and found that overweight and obese men coupled with normal- weight females had an odds ratio for reduced fertility of 1.18 and 1.53, respectively. A further observation was that couples where both parents were overweight or obese, the odds ratios for reduced fertility were 1.41 and 2.74, respectively [73]. Obese people have decreased gonadotropin levels, and increased circulating estrogen levels [74]. The increase in estrogen is likely secondary to peripheral aromatization of androgens from cholesterol in the adipose tissue. A hypogonadotropic hypogonadism state is created due to estrogen

Metabolic disorders, including diabetes, obesity, and hyperlipidaemia plays a significant role in the development of female-specific reproductive health issues, which have a significant impact on public health. MetSy also increases the risk of reproductive cancers such as, breast, endometrial, bladder and cervical cancers [73]. Obesity particularly impacts women of reproductive age, as it is associated with an increased risk of infertility and adverse obstetric outcome such as miscarriage, stillbirth, birth defects and cesarean section [70, 75, 76]. MetSy can affect women's reproductive health and fertility directly or indirectly by interfering with the hypothalamic – pituitary – gonadal (HPG) axis function. MetSy creates conditions of negative energy balance and metabolic stress which cause hypogonadism by suppressing the expression of the hypothalamic

In addition to the effect of peripheral aromatization which create the hypogonadotropic hypogonadism state in obese women, a lack of residual insulin secretion in diabetes is also associated with the status quo [79]. The hypothalamic origin of the decreased levels of gonadotropin in amenorrhoeic and diabetic patients are related to a toxic effect of hyperglycaemia on the neurons of the hypothalamus

Adrenarche is the puberty of the adrenal gland. Pubarche is denoted by the appearance of pubic hair and or axillary hair. Premature adrenarche in girls is when pubarche occurs before age 8 years in girls and 9 years in boys. The chief hormonal products of adrenarche are DHEA and DHEAS produced from zona reticularis. Premature adrenarche represents an early clinical feature of MetSy (obesity, hypertension, dyslipidaemia, insulin resistance) for some girls. Conceivably the early recognition of these children will permit allow early intervention, such as lifestyle modifications, including dietary, activity level intervention with possibility of using insulin-sensitizing agents in some individuals. Premature pubarche due to premature adrenarche and hyperinsu-

linemia may precede the development of ovarian hyperandrogenism [81].

*DOI: http://dx.doi.org/10.5772/intechopen.95971*

negative feedback onto the hypothalamus [74].

KiSS/kisspeptin [77, 78].

*10.3.1 Premature adrenarche in girls*

**10.3 Metabolic syndrome and female reproductive health**

leading to reduced LH response to GnRH stimuli [80].

**Figure 1.** *(vivo.colostate.edu).*

*Lifestyle and Epidemiology - The Double Burden of Poverty and Cardiovascular Diseases...*

of testosterone. Theca cells in the ovary respond to LH stimulation by secretion of testosterone, which is converted into estrogen by adjacent granulosa cells. In females, the LH surge leads to ovulation of mature follicles on the ovary and later to form corpus luteum, which secrete the steroid hormones progesterone and oestradiol. In the event of pregnancy progesterone is necessary for the maintenance of that

The FSH is responsible for the maturation of ovarian follicles. Administration of FSH to humans and animals induces "superovulation", an increased number of mature gametes. FSH is also critical for spermatogenesis and sperm cell maturation

LH and FSH secretion is under the influence of gonadotropin-releasing hormone (GnRH, also known as LH-releasing hormone). GnRH is a ten amino acid peptide that is synthesized and secreted from hypothalamic neurons and binds to receptors

As depicted in **Figure 1** below, GnRH stimulates secretion of LH, which in turn stimulates gonadal secretion of the sex steroids testosterone, estrogen and progesterone. In a classical negative feedback loop sex steroids(oestrogens, progesterone, testosterone) inhibit secretion of GnRH and also appear to have direct negative

This regulatory loop leads to pulsatile secretion of LH and, to a much lesser extent, FSH. The number of pulses of GnRH and LH varies from a few per day to one or more per hour. In females, pulse frequency is clearly related to stage of

Several hormonal substances such as inhibin and activin from the gonads, which selectively inhibit and activate FSH secretion from the pituitary, influence GnRH secretion, and positive and negative control over GnRH [69]. Thus gonadotropin secretion is actually considerably more complex than depicted in

**198**

**Figure 1.** *(vivo.colostate.edu).*

pregnancy.

at the Sertoli cells.

on gonadotrophs.

the cycle.

**Figure 1** below.

effects on gonadotrophs.

*10.1.2 Follicle-stimulating hormone*

*10.1.3 Control of gonadotropin secretion*
