What Are Sex Hormones?
The endocrine system produces chemical substances called hormones and releases them into the bloodstream. These hormones act as messengers between the body's cells and help carry out the body’s functions. Sex hormones play an essential role in sexual development and reproduction. Sex hormones are produced mainly by the adrenal glands and ovaries (in females) and testis (in males). Besides the main functions, sex hormones also play a vital role in different body functions.
What Are the Types of Sex Hormones?
In females, the adrenal glands and ovaries produce sex hormones. The most important female sex hormones are:
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Estrogen.
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Progesterone.
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Testosterone.
1. Estrogen:
Estrogen is the most important female sex hormone. The ovaries produce a more significant part of it. The adrenals and the fat cells produce lesser amounts. Placenta also produces estrogen in pregnancy.
Types of Estrogen:
The three types of estrogen are:
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Estrone (E1) is the form of estrogen that the body produces after menopause.
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Estradiol (E2) is the most potent type produced during the reproductive years.
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Estriol (E3) is the primary estrogen form during pregnancy.
What Are the Functions of Estrogen?
Estrogen plays a pivotal role in reproduction and sexual development. Apart from the above functions, it also has a role to play in various other body functions. The important functions where estrogen plays a role are:
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Pregnancy.
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Menstruation.
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Skin conditions.
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Hair fall.
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Cardiovascular functions.
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Urinary tract functions.
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Musculoskeletal functions.
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Brain functions.
Normal Ranges of Estrogen:
The estrogen levels vary highly during different phases of a person’s life and from person to person. The following are considered the normal ranges of estrogen determined by blood tests.
- Premenopausal adult female: 15-350 pg/mL.
- Postmenopausal adult female: <10 pg/mL.
- Adult male: 10-40 pg/mL
(pg/mL refers to picograms per milliliter).
2. Progesterone:
Progesterone is the crucial hormone of pregnancy. It is produced by the ovaries, placenta, and adrenal glands. Post ovulation, the ovaries release progesterone at its peak levels during pregnancy.
What Are the Functions of Progesterone?
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Support during pregnancy.
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Prepares the uterine lining to receive the fertilized egg.
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Suppress estrogen levels after ovulation.
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Prepares the body for pregnancy.
Low progesterone levels can lead to difficulty in getting pregnant, irregular periods, and risk of complications during pregnancy.
Normal Ranges of Progesterone:
Simple blood tests determine progesterone levels. Normal ranges are as follows:
- Before puberty: 0.1 to 0.3 ng/mL.
- First or Follicular stage of menstrual: 0.1 to 0.7 ng/mL.
- During ovulation: 2 to 25 ng/mL.
- First trimester of pregnancy: 10 to 44 ng/mL.
- Second trimester of pregnancy: 19.5 to 82.5 ng/mL.
- Third trimester of pregnancy: 65 to 290 ng/mL.
(ng/mL refers to nanograms per milliliter).
3. Testosterone:
Testosterone, the primary sex hormone in males, is also secreted in meager amounts in females. It is produced by the ovaries and adrenal glands.
What Are the Functions of Testosterone?
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Sexual desire.
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Menstrual cycle.
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Muscle and bone strength.
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Production of red blood cells (RBCs).
Normal Ranges of Testosterone:
The levels of testosterone in the body are determined by blood tests. The average values in females are 15 to 70 ng/dL (nanograms per deciliter).
What Is the Role of Sex Hormones During Different Phases?
Sex hormones are essential in various phases of a woman’s life. The levels of these hormones keep changing throughout. Puberty, menstruation, pregnancy, breastfeeding, and menopause are the different stages in which the levels vary greatly.
What Is the Role in the Pubertal Phase?
The average pubertal age in females is 8 to 13 years. During this time, the pituitary gland produces luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH, in turn, stimulate the production of sex hormones, mainly estrogen. Secondary sexual characteristics develop as a result of the increase in hormonal levels. The following changes occur in girls:
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Growth and development of breasts.
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Growth of pubic and armpit hair.
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Start of the menstrual cycle.
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Development of acne due to increasing oil production.
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Increase in height.
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An increase in fat, especially in the pelvic and thigh region.
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Widening of the pelvis and hips.
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Maturation of the vagina, ovaries, and uterus.
What Is the Role in the Menstrual Phase?
Menstruation begins in most females two to three years after the start of breast development. The average age is 10 to 16 years. The menstrual cycle lasts for 28 days typically but can range from 24 to 38 days. The menstrual period includes three phases - follicular, ovulatory, and luteal.
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Follicular Phase:
The new menstrual cycle begins on the first day of bleeding. The uterus that has been thickened for receiving a probable fertilized egg begins to shed the lining in the form of blood. Mood swings and irritable behavior are common during the follicular phase as estrogen and progesterone are at low levels.
The pituitary gland also releases FSH during this phase which stimulates the growth of follicles in the ovaries. Each follicle contains an egg, however, due to lesser estrogen and progesterone levels, only one follicle growth becomes prominent, and hence one egg is released at the end of the phase. The follicular phase typically lasts two weeks.
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Ovulatory Phase:
This phase follows the follicular phase. During this phase, an increase in LH causes the follicle to burst and release the egg from the ovary. After leaving the ovary, the egg survives for 12 to 24 hours. Fertilization of the egg is possible only during this period.
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Luteal Phase:
The egg travels from the ovary to the uterus through the fallopian tubes. After reaching the uterus, it attaches to the uterine wall, where fertilization can occur. Bursting of the follicle to release the egg stimulates progesterone production. Progesterone prepares the uterus to sustain the fertilized egg.
An unfertilized egg causes a decline in estrogen and progesterone levels that causes the egg and the uterine lining to exit the body. This is the end of the present menstrual cycle and the beginning of the next one.
What Is the Role in Sexual Arousal?
Sex hormones play an important role in the development of sexual desire. Higher estrogen levels cause an increase in vaginal lubrication and sexual desire. Increased progesterone levels decrease the sexual urge. The role of testosterone in influencing sexual urge is not known completely. However, low levels of testosterone are believed to lower the desire for sex.
What Is the Role in Pregnancy?
Pregnancy is initiated by the implantation of the fertilized egg into the uterine wall. Implantation releases hormones, progesterone, relaxin, and human chorionic gonadotropin (hCG). Progesterone levels rise rapidly in the first few weeks, causing cervix thickening and mucus plug formation. Relaxin prevents the uterus from contracting till the pregnancy completes.
Human chorionic gonadotropin (hCG) causes early pregnancy symptoms like nausea and vomiting.
Estrogen and progesterone levels keep rising in the second trimester as well. The placenta produces a hormone, namely human placental lactogen (hPL), that nourishes the fetus and stimulates milk production. Completion of pregnancy and start of breastfeeding lowers the levels of estrogen that can prevent ovulation from occurring.
What Is the Role in Menopause?
When a woman does not get her menstrual periods for one full year, she is believed to have entered menopause. The levels of estrogen fall considerably, which leads to vaginal dryness, loss of libido, irregular periods, mood swings, and increased risk of bone and heart diseases.
What Happens When There Is an Imbalance of Sex Hormones?
Though the hormonal levels fluctuate regularly, a long-term imbalance requires medical intervention. Obesity, polycystic ovary syndrome (PCOS), stress, and ovarian cancer are the important reasons for a hormonal imbalance to occur.
The signs and symptoms include:
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Facial hair.
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Acne.
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Irregular periods.
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Weight gain.
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Mood swings.
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Tiredness.
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Anxiety and depression.
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Insomnia.
Conclusion:
Female sex hormones play an essential role in fertility and reproduction. Though the levels fluctuate at various phases, long-term fluctuations need to be monitored and treated at the earliest. It helps in maintaining a balance between the physiological and psychological well-being of the patient.
