GnRH signals the pituitary gland to release two puberty hormones into the bloodstream: FSH and luteinizing hormone (LH). FSH and LH tell the testes and ovaries to make hormones that bring about changes during puberty. Human sex hormones work closely with one another.
Mean LH and FSH concentrations both increase gradually through pubertal development in concert with sex steroid concentrations, although LH rises to a greater extent, due to differences in feedback mechanisms and sensitivity for these two hormones, as described above.
In children, FSH levels are usually low until puberty, when levels begin to rise. In girls, it helps signal the ovaries to make estrogen. In boys, it helps signal the testes to make testosterone.
Luteinizing hormone in infants and children
During puberty, LH stimulates both ovaries and testes to make more testosterone. In the ovary, testosterone is then converted into estrogen. These hormones cause changes related to sexual development.
Before puberty - 0 to 5.0 mIU/mL (0 to 5.0 IU/L) During puberty - 0.3 to 10.0 mIU/mL (0.3 to 10.0 IU/L) Adult - 1.5 to 12.4 mIU/mL (1.5 to 12.4 IU/L)
§ In most laboratories, the upper limit of normal for LH after GnRH stimulation is 3.3 to 5.0 mIU/mL. Stimulated LH concentrations above this normal range suggests CPP. ¥ A peak stimulated LH:FSH ratio <0.66 usually suggests nonprogressive precocious puberty, whereas a ratio >0.66 is typically seen with CPP.
It has been well documented that both LH and inhibin B levels increase during puberty, particularly early puberty. Mean circulating levels of LH, together with the other gonadotropin, follicle-stimulating hormone (FSH), increase beginning before physical changes of puberty begin (11).
Luteinizing hormone (LH) plays a key role in gonadal function. LH in synergy with follicle stimulating hormone (FSH) stimulates follicular growth and ovulation. Thus, normal follicular growth is the result of complementary action of FSH and LH.
FSH levels are normally low in children. As puberty approaches (usually between ages 10 and 14), the hypothalamus produces gonadotropin-releasing hormone (GnRH), which triggers FSH and LH. This begins the changes toward sexual maturity and development.
When your body reaches a certain age, your brain releases a special hormone that starts the changes of puberty. It's called gonadotropin-releasing hormone, or GnRH for short.
At puberty the hypothalamic pituitary unit begins to function like that of an adult. The hypothalamus begins to secrete increased amounts of gonadotropin-releasing hormone or GnRH in a pulsatile manner and the pituitary responds by secreting increased amounts of gonadotropins, FSH and LH in a pulsatile manner.
A high FSH level suggests that your ovaries may not have very many eggs left. If high FSH levels occur alongside high LH secretion, your ovaries may have stopped working normally – which may indicate a depleted ovarian reserve, a sign that you may be nearing menopause.
Usually, in healthy women, the ratio between LH and FSH usually lies between 1 and 2. In polycystic ovary disease women, this ratio becomes reversed, and it might reach as high as 2 or 3 (8). As a result of raised LH/FSH ratio, ovulation does not occur in polycystic ovary disease patients (9).
In both males and females, FSH and LH are rhythmically secreted to control reproductive physiology. In males, these hormones drive the synthesis of testosterone and the production and development of sperm. In females, FSH triggers follicle maturation, and a sudden surge in LH drives ovulation.
The rise in FSH and LH with increasing age is consistent with the decline in testosterone, assuming normal operation of the feedback pathway by which low testosterone level signals the hypothalamic-pituitary axis to release FSH and LH.
For girls who are yet to go through puberty (aged around 1–10 years), the normal range is 0.03–3.9 IU/L.
< 1 year old: < 0, 02 – 5.0 IU/L 1-8 years old: < 0.02 – 0.5 IU/L 9-10 years old: < 0.02 – 3.6 IU/L 11-13 years old: 0.1 – 5 ,7 IU/L 14-17 years old: 0.8- - 8.7 IU/L In young children, high levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are associated with growth.
Normal Results
Before menopause: 5 to 25 IU/L. Level peaks even higher around the middle of the menstrual cycle. Level then becomes higher after menopause: 14.2 to 52.3 IU/L.
The vulva, vagina and nipples get bigger and the breasts begin to develop, sometimes unevenly. Other changes include pubic hair appearing and a vaginal discharge – an increase in the mucous produced in the vagina. They will also start menstruating or having their period during this time.
In Stage 4, puberty hits full stride. Between the ages of 10 and 15: Their breasts continue growing, and their nipples start to protrude. Pubic hair is still in a triangle, and there are now too many hairs to count.
The average age for girls to start puberty is 11, while for boys the average age is 12. But it's perfectly normal for puberty to begin at any point between the ages of 8 and 13 in girls and 9 and 14 in boys.