Sex Differentiation and Puberty Flashcards
List 3 measurements used to assess the adolescent growth spurt.
1 - Time of minimum growth velocity (the age immediately preceding the growth spurt).
2 - Peak height velocity (PHV - the highest rate of growth).
3 - Time of decreased growth velocity (the age immediately following the growth spurt).
On average, when do boys experience the growth spurt relative to girls?
On average, boys experience the growth spurt two years later than girls.
What is the difference in average height gain during puberty between boys and girls?
On average, boys gain 28cm, whereas girls gain 25cm during the growth spurt.
List 5 physiological factors that are required for normal puberty.
Normal puberty needs:
1 - Normal XX or XY chromosomes.
2 - A normal hypothalamus.
3 - A normal pituitary.
4 - Normal ovarian / testicular function.
5 - Normal responsiveness of tissues to hormones.
How does gonadotropin secretion change throughout the circadian rhythm in early puberty?
In early puberty, FSH and LH secretion is low throughout the day and becomes moderately pulsatile at night.
How does gonadotropin secretion change throughout the circadian rhythm in mid-puberty?
- In mid-puberty, LH secretion is constant / non-pulsatile but is moderately increased from the basal level of secretion in earlier puberty.
- In mid-puberty, FSH secretion is still pulsatile at night, but the pulses are greater. Some lesser pulses also start to occur in the day.
How does gonadotropin secretion change throughout the circadian rhythm in mid-puberty?
- In late puberty, LH secretion is constant / non-pulsatile but is significantly increased from the basal level of secretion in earlier puberty.
- In late puberty, FSH secretion is pulsatile throughout the day, and the pulses are greater.
What is hypogonadotropic hypogonadism?
Hypogonadotropic hypogonadism is a condition in which there is a decrease in activity of the gonads due to a failure of secretion of gonadotropins.
List 2 proteins that contribute to hypogonadotropic hypogonadism.
What is the function of these proteins?
1 - GPR54 (a receptor).
2 - Kisspeptin (a ligand for GPR54 secreted by KISS neurones).
- These proteins initiate gonadotropin secretion at puberty.
What is the true / central precocious puberty?
How does it differ from precocious pseudopuberty?
- True / central precocious puberty is early onset puberty due to a defect (increased) in GnRH or gonadotropin secretion (GnRH-dependent).
- In contrast to precocious pseudopuberty, where the defect is further down, e.g. in the gonads, adrenal glands liver, etc (GnRH-independent).
How is a differential diagnosis of true precocious puberty and precocious pseudopuberty carried out?
- In puberty, the dominating gonadotropin is LH.
- Therefore, with administration of GnRH, both LH and FSH will increase, but the LH:FSH ratio will be >1.
- If the patient suffers from true / central precocious puberty, the pituitary will hypersecrete FSH and LH in response to GnRH. The LH:FSH ratio will be significantly >1.
- If the patient suffers from precocious pseudopuberty, the pituitary will respond with a normal increase in secretion of FSH and LH in response to GnRH. The LH:FSH ratio will not be >1.
How are the clinical signs of true precocious puberty different from that of precocious pseudopuberty?
- In true precocious puberty, the signs of early pubertal development are in agreement with other features of puberty, e.g. pubic hair growth, growth spurt etc.
- In precocious pseudopuberty, the signs of early pubertal development are in isolation, and are not in agreement with other features of puberty.
- This is because if the problem is central, then all peripheral structures will be affected because the hypersecreted FSH and LH will affect the whole circulation.
List 3 causes of true precocious puberty.
Causes of true precocious puberty:
1 - CNS tumours.
2 - Developmental disorders.
3 - Encephalitis.
List 3 causes of precocious pseudopuberty.
Causes of precocious pseudopuberty.
1 - Congenital adrenal hyperplasia.
2 - Non-central gonadotropin-secreting tumours, e.g. choriocarcinoma and chorioepithelioma.
3 - McCune-Albright syndrome.
What is McCune-Albright syndrome?
- McCune–Albright syndrome is a genetic disorder affecting the bone, skin and endocrine systems.
- It is a mosaic disease caused by a mutation to the Gs alpha subunit.