Week 1: puberty

Question 1

juvenile reproductive development

Answer 1

• Birth to 6 months: boys have surge in testosterone. Unknown reason.
• childhood: steroid independent suppression of GnRH. LH/FSH low even in agonadal individuals. There are other factors that limit reproduction during childhood. Children acquire sensitivity to gonadal steroid feedback as they approach puberty

Question 2

menstruation vs ovulation

Answer 2

• earliest menstrual cycles are often anovulatory
• follicles develop and secrete estrogen but degenerate before ovulation. With atresia, estrogen levels fall and endometrial lining is shed.

Question 3

Hormonal changes during puberty

Answer 3

• initial stages of puberty: increased pulsatile gonadotropin secretion during sleep
• steroid independent mechanisms no longer suppress GnRH. Small amounts of steroids no longer able to inhibit GnRH.
• later GnRH pulses are expressed day and night
• even before increase in gonadotropins, androgen begins being secreted from adrenal glands and cause growth of pub and axillary hair
• GH and sex steroids work together to cause growth spurt. Gonadal steroids also stop growth by causing closure of epiphyseal plates

Question 4

What controls onset of puberty?

Answer 4

• before puberty, today can respond to gonadal steroids, the gonad can produce steroids in response to gonadotropins, and GnRH neurons are capable of pulsatile GnRH release. These are not limiting factors
• Gonadostat hypothesis: There is a reduction in sensitivity to inhibitory steroid feedback. However, neural basis of steroid dependent/independent inhibition of GnRH is unknown
• nutrition/growth: girls with inadequate nutrition/excessive exercise have delayed menses. Correlation between nutrition/body weight/fat and timing of puberty.

Question 5

Kallman’s syndrome

Answer 5

• hypogonadal and anosmic
• failure of migration of GnRH neurons from olfactory placed
• Rx
• women: put on OCPs, and give pulsatile GnRH if want to be fertile
• men: long active testosterone supplementation. Give GnRH for fertility

Question 6

Leptin deficiency and puberty

Answer 6

• leptin deficiency patients had hypogonadism and retarded sexual development
• when given leptin, increase in GnRH/LH secretion during puberty
• leptin is one of the signals for maturation, but no the only signal, because when given in a younger leptin deficient patient, there is no increase in LH