Hormones are the chemical messengers secreted by endocrine glands directly into systemic blood circulation. They control distinct body functions. Each hormone has its own designated biological role. Hormones are diverse and are known to control different metabolisms, growth, development, repair, reproduction as well as stress. On a whole, hormones control the emotional as well as the physical health of the human body. Sex hormones perform functions related to reproduction and sexual behaviour. The male sex hormones are especially concerned with the development of male sex organs, secondary sexual characteristics and reproduction.
Male sexual characteristics and reproduction are controlled by male sex hormones namely testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEA-S) and androstenedione. Generally, the steroidal sex hormones are called androgens.
Testes, adrenal glands, prostate glands and peripheral tissues contribute to the male sex hormone secretion.
In the adult stage, testosterone is the chief male sex hormone and is secreted by the interstitial Leydig cells of the testes.
The first secretion of testosterone occurs at the fetal stage itself. Testes cords are fetal testicles within which the testosterone secreting fetal Leydig cells lie.
The outer layer of adrenal glands is the adrenal cortex. As the males reach 8 years of age, the adrenal cortex starts to secrete androgens that further continue till puberty. However, the adrenal secretion is transcended by the testicular secretion with increasing age.
The adrenal cortex secretes testosterone precursors like Dehydroepiandrosterone (DHEA), and Dehydroepiandrosterone sulphate (DHEA-S).
Secretion of precursors also adds up the testosterone levels however, it is far lower than the principal secretion from the testes.
Androstenedione is secreted by the adrenal glands and testes. It is rapidly converted to testosterone.
Dihydrotestosterone (DHT) levels are contributed by the testes, prostate glands and peripheral tissues of the body majorly from the testosterone conversion.
The adrenocorticotrophic hormone controls the adrenal secretion while the follicle-stimulating hormone (FH) and luteinising hormone (LH) control the testicular secretion.
The pituitary secretion of both FH and LH is in turn controlled by the gonadotrophin-releasing hormone (GnRH) secreted by the hypothalamus.
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In the fetal stage, it causes the development of the male reproductive system.
Throughout adult life, testosterone causes spermatogenesis (the process of sperm formation from the primordial germ cells) and enhances libido for reproductive health in males.
It also causes penis and testicular enlargement.
Apart from these, testosterone is involved in the development of male characteristics like deepening of voice, and body hair.
During puberty, testosterone causes increased fat deposition, skeletal muscle growth, and increased bone density all of which lead to the development of masculine features.
Fetal DHT is involved in sex organ differentiation.
In the puberty as well as adult stage, DHT is associated with prostate growth and the development of male sexual characteristics including the growth of facial hair.
It is an immediate precursor for testosterone and majorly contributes to testosterone levels in males.
It is administered by athletes and bodybuilders for its anabolic effects on body mass building. It is a banned steroid in some nations.
Dehydroepiandrosterone and Dehydroepiandrosterone sulphate are precursors of testosterone.
The male sex hormones are involved in maintaining the reproductive health of males, and changes in their levels are to be understood well.
Testosterone levels are measured through blood tests and most commonly they do not fluctuate as the female sex hormones do in women. Hypogonadism in males is characterised by low testosterone secretion from the testes. Hypoadrenalism is the low androgen levels due to low adrenal cortical secretions.
Both of them can be because of impairment in testicular or adrenal tissues that can be due to a multitude of reasons like −
Testicular injury, trauma or infection.
Testicular failure due to autoimmune diseases.
Adrenal cancers.
Chemotherapy treatment.
Tumours in the pituitary gland or hypothalamus.
Head injury or brain surgery.
Ageing.
Delay in puberty.
Hypergonadism is the higher secretion of sex hormones resulting in prevailing high testosterone levels. Higher adrenal cortical androgen secretion is medically considered hyperandrogenism Both the conditions can be due to −
Testicular or adrenal tumours (even benign tumours are capable of rising testosterone levels)
Steroid usage
Fluctuations in male hormone levels have potential side effects.
Hypogonadism and hypoadrenalism lead to low male sex hormone levels with possible side effects like −
Reproductive problems like lowered libido, erectile dysfunction and infertility.
Bone problems like osteoporosis.
Decreased muscle mass and strength.
Thinning body hair.
Anemia to some extent.
General fatigue, irritability, moodiness, lack of ability to concentrate.
Sleep problems.
Hypergonadism and hyperadrenalism lead to high male sex hormone levels with possible side effects. High testosterone levels lead to −
Reproductive problems like low sperm count and shrunken testes causing infertility.
Increased muscle mass.
Aggressive and irritable moods.
Facial skin becomes oily and acne prone.
Increased sleep apnea.
Increased bad cholesterol levels with the risk of developing heart diseases.
Male sex hormones are primarily concerned with the maintenance of reproductive health as well as the development of male sexual characteristics. The male sex hormones include testosterone, dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEA-S) and androstenedione. Among all of them, testosterone is the principal male sex hormone primarily controlling the development of the male reproductive system and spermatogenesis. Male sex hormones are secreted by the testes, adrenal cortex, prostate glands, and peripheral tissues. Their secretion begins at the fetal stage itself. Development of sex organs and reproductive tract, body hair, deepening of the voice, increasing bone density and body musculature are all concerned with the male sex hormones.
Q1. How is testosterone synthesized?
Ans: Testosterone is derived from cholesterol and is a steroid hormone. Its synthesis takes place in Leydig cells of testes. The follicle-stimulating hormone (FH) and luteinising hormone (LH) control the synthesis and secretion of testosterone.
Q2. Do females secrete testosterone?
Ans: Female ovaries secrete small amounts of testosterone. However, increased levels than the normal range can lead to irregular menstrual cycles, acne development, and virilising effects in females.
Q3. What is the location of the adrenal cortex?
Ans: Adrenal glands are triangular-shaped glands on the top of the kidneys. The outer layer of adrenal glands is the adrenal cortex which is composed of three layers called zona glomerularis, zona fasciculata and zona reticularis.
Q4. What is testosterone therapy?
Ans: Hypogonadism characterised by low testosterone levels is treated with testosterone therapy. In this process, testosterone is supplemented or topically applied in the form of gels. It results in increased libido and has positive effects on muscle mass, bone density and strength.
Q5. Why is androstenedione a banned drug?
Ans: Androstenedione is an immediate precursor for testosterone and has activities related to increasing body mass, reducing body fat and increasing energy levels. It is often considered a performance-improving drug and for this reason, it is a banned drug for athletes.
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