What happens during normal puberty?
The physical features of males and females can be divided into two main groups: the primary sexual characteristics and the already briefly mentioned secondary sexual characteristics. The first group is directly involved in sexual reproduction, whilst the second group is not, indicating that puberty has occurred due to the action of gonadal hormones. The primary and secondary sexual characteristics are listed in Table 1.Puberty is not something which happens overnight; it often takes three or four years to complete. It is the transition period during which boys acquire the physical characteristics of adult men and girls those of adult women. Research has shown that generally, girls reach puberty by the age of 15, a year or two earlier than boys.
Normally, special cells in the hypothalamus secrete a hormone called GnRH, the "Gonadotrophin Releasing Hormone". GnRH is then delivered to the pituitary gland via capillaries in the pituitary stalk. As its name suggests, GnRH releases other hormones (the gonadotrophins) from the pituitary gland. The suffix -trophin means "the nourishment of" and so a literal translation of "gonadotrophin" is "the nourishment of the gonads". There are two main gonadotrophins: LH and FSH, the "Luteinizing Hormone" and "Follicle Stimulating Hormone", respectively. In some countries, GnRH is also known as LHRH, the "Luteinizing Hormone Releasing Hormone", although this can be a little misleading because it is not only LH, but also FSH which is released by GnRH / LHRH.
Function of the gonadotrophins in men during and after puberty
LH and FSH target different cells with different functions in the testes. In simple terms, LH encourages masculinity and FSH promotes fertility.In the normal male, LH targets special cells called Leydig or interstitial cells and it is here that almost 95% of the main male sex hormone testosterone is made. The remaining 5% of testosterone is manufactured by the adrenal glands above the kidneys (answer to Question 3). Testosterone is responsible for the development of the male body's secondary sexual characteristics during puberty (Table 1). FSH, with a little help from some testosterone, stimulates the production of sperm cells, a process known as spermatogenesis. Sperm cell production can take up to 76 days to be completed from beginning to end.
