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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. 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.
Find and instantly book your next health appointment with Healthengine Find health practitioners Changes to the body during pubertyTestosterone 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. Changes in hair distribution 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. Changes to the voice The larynx enlarges during puberty, initially resulting in a cracking voice, but gradually resolving into a deeper typically adult masculine voice. Changes to the skin 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. Changes to the bone 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. Changes to the blood Testosterone stimulates the production of red blood cells, so that the quantity and proportion of red blood cells in males is higher than females. Changes to the brain 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 pubertyDuring 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. Early puberty 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 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 puberty 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 pubertyPrecocious 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 pubertyWhen 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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Puberty is the term used to describe the developmental changes a child undergoes to become sexually mature and physiologically ready for reproduction. It normally begins between the ages of 8-14 in females, and between the ages of 10-16 in males. In this article, we will discuss the hormonal and physical changes that occur during puberty in boys and girls and its clinical relevance. Hormonal ChangesPuberty and the reproductive system are controlled by the hormones of the Hypothalamic-Pituitary-Gonadal (HPG) axis. The hypothalamus releases Gonadotropin Releasing Hormone (GnRH) in a pulsatile manner, which stimulates the release of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) from the anterior pituitary gland. FSH and LH act on the gonads (ovaries/testicles) to stimulate the synthesis and release of the sex steroid hormones (oestrogen/progesterone and testosterone) and support gametogenesis. These sex steroids exert many effects on the reproductive system and feedback negatively on the hypothalamus and the pituitary gland to ensure that circulating levels remain stable. During childhood the levels of FSH and LH in the body are low. This is thought to be due to the slow cycling of the GnRH pulse generator in the hypothalamus. Approximately a year before the first physical changes of puberty there is a rise in the pulsatile release of FSH and LH, as a result of the GnRH pulse generator being released from CNS inhibition. The rise in FSH stimulates an increase in oestrogen synthesis and oogenesis in females and the onset of sperm production in males. The rise in LH stimulates an increase in production of progesterone in females and an increase in testosterone production in males. As a result of these hormonal changes the physical changes associated with puberty begin to develop. The speed of development varies greatly between children, as genetic factors contribute. It is also suggested that body weight influences the onset of puberty. Physical ChangesPuberty in FemalesThelarcheThe first sign of puberty in girls is the beginning of breast development (thelarche). This typically occurs at around age 9-10. Breast buds appear as small mounds with the breast and papilla elevated. Tanner staging is used to assess breast size/development with stages I-V (shown below). The breasts consist of lobulated glandular tissue embedded in adipose tissue, separated by fibrous connective tissue. Following the clearance of placental oestrogens after birth, the breasts are in a dormant stage until puberty. In this dormant stage there are only lactiferous ducts with no alveoli. At puberty the increase in ovarian oestrogens causes the development of the lactiferous duct system as the ducts grow in branches with the ends forming the lobular alveoli (small, spheroidal masses). Mediated by progesterone, these lobules will increase in number through puberty. The breasts continue to increase in size following menarche due to increased fat deposition. Throughout the menstrual cycle, oestrogen and progesterone affect the breast size and composition. [caption id="attachment_14859" align="aligncenter" width="266"] PubarcheThe second sign of puberty in girls is typically the growth of hair in the pubic area. The hair initially appears sparse, light and straight; however, throughout the course of puberty it becomes coarser, thicker and darker. Approximately 2 years after pubarche, hair begins to grow in the axillary area as well. In both sexes, hair growth is a secondary sexual characteristic mediated by testosterone. MenarcheMenarche is the first menstrual period and marks the beginning of the menstrual cycles. It normally occurs around 1.5-3 years after thelarche and is due to the increase in FSH and LH. The menarche process typically occurs at ~12.8 years (+/- 1.2 years) for Caucasian girls and 4-8 months later for African-American girls. More information can be found in our menstrual cycle article. Puberty in MalesGenital changesThe first sign of puberty in boys is the increase in testicular size. The increased LH stimulates testosterone synthesis by Leydig cells and the increased FSH stimulates sperm production by Sertoli cells. Spermatogenic tissue (Leydig cells and Sertoli cells) makes up the majority of the increasing testicular tissue. The progression of testicle size can be measured by tanner staging from stage I to stage V. As the testicles increase in size the scrotal skin also grows and becomes thinner, darker in colour and starts to hang down from the body. It also starts to become spotted with hair follicles (these appear as little lumps.) Approximately a year after the testicles begin to grow, boys can experience their first ejaculation because the testicles are now producing sperm as well as testosterone. The first ejaculation marks the theoretical capability of procreation. However, on average fertility is reached one year after first ejaculation. The growth of the penis follows the testicular enlargement. The penis first grows in length. Then the width of the penis increases as the breadth of the shaft increases. The glans penis and corpus cavernosum also enlarge. PubarcheAnother pubertal sign in boys is the growth of pubic hair at the base of the penis (pubarche). This often occurs alongside testicular growth. Pubic hairs will initially be light coloured, straight and thin; however, as puberty progresses they become darker, curlier, thicker and more widely distributed. Approximately 2 years following pubarche, hair also begins to grow on the legs, arms, axillae, chest and face. [caption id="attachment_14860" align="aligncenter" width="185"] Growth spurt (Males and Females)The pubertal growth spurt is the product of a complex interaction between the gonadal sex steroids (oestradiol/testosterone), GH and insulin-like growth factor 1 (IGF-1). GH levels will rise in puberty due to the increase in sex steroids (testosterone which has been converted to oestradiol) and their positive effect on the pulsatile release of GH from the anterior pituitary gland. A rise in GH causes a rise in the anabolic hormone IGF-1, which causes somatic growth via its metabolic actions (e.g. increases trabecular bone growth.) Following the peak of the growth spurt in males, the larynx and vocal cords (voicebox) enlarge, and the boy’s voice may ‘crack’ occasionally as it deepens in pitch. [start-clinical] Clinical Relevance - Precocious PubertyWe define precocious puberty is as the appearance of secondary sexual characteristics before the age of 8 in girls or before the age of 9 in boys. There are a variety of causes/types:
Precocious puberty may either be isosexual (early sexual development consistent with the genetic and gonadal sex of the child) or contrasexual (early sexual development associated with feminisation of a male or virilisation of a female). Clinical Relevance - Delayed/Absent PubertyWe define delayed or absent puberty as the absence of secondary sexual characteristics by the age of 13 in girls or 16 in boys. There are various causes:
Doctors can treat severe delayed/absent puberty with carefully controlled hormonal replacement therapy. [end-clinical] |
What happens to male hormones during puberty?
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