What is puberty?
Nearly all the organ systems in the human body begin to grow and develop after birth. However, the reproductive system remains inactive for several years. While it is dormant, the brain secretes very small amounts of reproductive hormones (gonadotrophins), preventing any sexual development from occurring. When boys reach the age of about 10-12, a surge of reproductive hormones are secreted by the brain, activating the reproductive system to prepare it for adult function. This surge is generally referred to as the onset of puberty and leads to the beginning of adult sexual life.
Puberty generally marks the beginning of adolescence, but the two things are not identical. Adolescence itself can be defined as the period between the onset of sex steroid secretion until full adult height is reached. Puberty is considered to be the beginning years of adolescence, and is complete when girls experience their first menstrual period or viable sperm is present in the ejaculate for the first time in boys. In Western nations such as Australia, girls attain puberty at around age 12, and boys at around 13.
Hormones and puberty
When the hypothalamus (a part of the brain) matures, it begins to produce and secrete a chemical called gonadotrophin releasing hormone (GnrH). GnRH then affects a different part of the brain, the pituitary, causing it to secrete two hormones crucial to normal reproductive function – lutenising hormone (LH) and follicle-stimulating hormone (FSH). These then stimulate cells in the testes, causing them to enlarge – the first sign of male puberty.
LH and FSH act on cells of the testes, causing them to produce testosterone and androgen-binding protein (ABP). ABP helps to raise testosterone levels in the testes. Testosterone plays an important role in the physical changes associated with puberty, and in testicular maturation. However, FSH needs to be present in sufficient amounts for testosterone to have its effects.
In addition to the enlargement of the testes, testosterone produces several other changes in the male body that are associated with puberty.
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Changes to the body during puberty
Testosterone produces the general distinguishing characteristics of the masculine body, causing changes to the sexual organs themselves as well as being responsible for secondary sexual characteristics:
Changes to the penis, scrotum and testes
These three organs enlarge by about 8 times by the age of 20 years. The internal ducts and glands of the reproductive system also increase in size during puberty. Males experience erections more frequently, and “wet dreams“, involuntary emissions of semen during sleep often accompanied by erotic dreams, often occur.
Hair grows around the pubic, underarm and facial areas. Hair around the pubic area generally extends upwards to the abdomen, sometimes reaching the belly button. Hair on the chest also develops, and less often on other regions of the body such as the back. Hair already present on most other portions of the body, such as the legs, becomes more prolific.
The larynx enlarges during puberty, initially resulting in a cracking voice, but gradually resolving into a deeper typically adult masculine voice.
The skin becomes thicker over the entire body. Sebaceous glands in the skin secrete increased amounts of sebum, especially on the face, which can lead to the development of acne. Acne is one of the most common features of male adolescence as the body is first exposed to increased testosterone. The skin normally adapts to these high testosterone levels over the years, gradually overcoming the acne.
Changes to muscle development and growth
Muscle mass increases. Males increase their muscle mass about 50% more than females. Increased protein is also found in non-muscular parts of the body.
The bones grow significantly thicker when circulating testosterone increases. The overall quantity of bone is increased, causing more calcium to be retained. Testosterone also acts on the pelvis, making it narrower and longer, causing a funnel-like shape, as opposed to the broad oval-like shape of the female pelvis, which is better suited to childbearing.
Testosterone stimulates the production of red blood cells, so that the quantity and proportion of red blood cells in males is higher than females.
Testosterone awakens the libido, or sex drive. In addition, many psychological changes during puberty occur that change the way a person’s mind works.
Psychological changes during puberty
During the course of puberty and adolescence, young people begin to shift away from concrete thinking to the more adult abstract thinking. Concrete thinking occurs when objects have to represent “things” or “ideas” for problem-solving. In contrast, abstract thinking is the ability to use internal symbols or images to represent reality. Young people are therefore able to move from thinking literally to thinking hypothetically about the future, and to assess multiple outcomes when faced with a problem.
During the early stages of puberty, concrete thinking still dominates but during this time early moral concepts begin to appear. Sexual orientation may also develop at this stage.
Mid-puberty, abstract thinking begins to feature more prominently. Many young people at this stage still have a sense of “invincibility” akin to that during childhood. The law is still generally identified as a guide to what is right, and its morality is not questioned. Fervent ideology may also start to develop, for example in the form of religious or political views.
Late in puberty, there is the development of complex abstract thinking and the identification of differences between law and morality, leading to questioning of the law and authoritative figures. Personal identity is also further developed.
Early onset of puberty – precocious puberty
Precocious puberty can occur as a result of abnormalities of the central nervous system that disrupt GnRH secretion, or it can be independent of GnRH secretion. The onset of puberty before the age of 9 generally defines precocious puberty in boys, and involves early physical changes of puberty, as well as accelerated linear growth and bone maturation. This can ultimately lead to a short adult stature because the bones stop growing early.
Delayed puberty
When a male shows no signs of entering puberty by the age of 14 (no enlargement of the testes), puberty is generally said to be delayed. Puberty can be delayed by a number of different factors, including inadequate nutrition, chronic illness, severe levels of stress and problems with interactions between the brain and the reproductive system.
More information
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For information on different types of contraception and related health issues, see Contraception. |
References
- Christie D, Viner R. Adolescent development. BMJ (Clinical research ed.) 2005; 330(7486): 301-4.
- Guyton AC, Hall JE. Textbook of Medical Physiology. 11th ed: Saunders 2005.
- Oerter Klein K. Precocious puberty: Who has it? Who should be treated? J Clin Endocrinol Metab. 1999; 84(2): 411-4.
- Saladin KS. Anatomy and Physiology: The Unity of Form and Function. 3rd ed. New York: McGraw-Hill 2004.
All content and media on the HealthEngine Blog is created and published online for informational purposes only. It is not intended to be a substitute for professional medical advice and should not be relied on as health or personal advice. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition. Never disregard the advice of a medical professional, or delay in seeking it because of something you have read on this Website. If you think you may have a medical emergency, call your doctor, go to the nearest hospital emergency department, or call the emergency services immediately.
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