1. What is puberty?
  2. How is the pubertal process activated?
  3. Which are the hormones active in this process?

What is puberty?

Puberty is the period of biological transition from infancy to adult age. The changes that occur at this time are related to the growing concentrations of sex steroid hormones. In females, the majority of pubertal changes are caused by the stimulation of oestrogens that matches with the onset of central puberty. A significant development occurs in the female reproductive system’s organs and causes anatomical changes that characterise reproductive maturity. All the biological changes that occur at this time are directly or indirectly related to the stimulation of sex steroid hormones. Many of the changes are of a functional nature and include important sexual characteristics. Body odours and acne, for example, are the result of the activation and increase of the secretion of apocrine and sebaceous glands. Body composition and fat distribution reflect metabolic changes induced by hormonal stimulation. In the same way, anthropometric changes are observable as sex steroids increase growth speed, with effects also on the bones. During this particular development stage, the reproductive organs that are not completely developed at birth undergo significant changes. This is true for both genders but is more complex in females that need to develop the capacity to provide an appropriate environment for foetal gestation and the source for child nutrition. The feminine organs primarily responsible for reproductive success include ovaries, uterus, vulva and breasts.

How is the pubertal process activated?

The pubertal process starts with the activation of the Hypothalamic-Pituitary-Gonadal axis (HPG). This process contributes to the foetus’s differentiation and sexual dimorphism but by the end of gestation, maternal oestrogen levels suppress further HPG activity of the foetus. After birth, a sudden increase of pubertal activity is observable, which is suppressed at 2 years of age until pubertal activity in late infancy. The trigger point for puberty is the production of the gonadotrophin-releasing hormone (GnRH) from a part of the brain called the hypothalamus, which causes the secretion of gonadotrophin, of the luteinizing hormone (LH) and of the follicle-stimulating hormone (FSH) from the pituitary gland or hypophysis.

Which are the hormones active in this process?

Once the serum gonadotrophines increase, they stimulate the gonadal tissue to produce sex steroids. FSH stimulation increases the activity of the microsomal aromatase of the ovarian granulosa cells; on the other side, the LH stimulates the production of androgens in the cells of the ovarian theca. At this point, these hormones circulate to promote pubertal changes in the whole body and carry out further gonadotrophin secretion.