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Physio 2 Sexual Differentiation & Maturation
Terms in this set (20)
What causes hypogonadism in Kallman's syndrome?
In Kallman's syndrome, an X-linked mutation/deletion causes GnRH neurons to fail to differentiate or migrate appropriately. This causes hypogonadism.
What are testosterone and dihydrotestosterone responsible for?
Testosterone: causes Wolffian duct Differentiation in male INTERNAL genitalia
Dihydrotestosteron: masculizes EXTERNAL genitalia
What does estradiol do?
Estradiol stimulates growth in both female internal structures and external genitalia, but does NOT cause differentiation
What do testosterone and estradiol do in the brain?
Cause differentiation of neural centers:
-cyclic ovarian function
-steroid negative feedback regulation of gonadotropin secretion
-Genomic steroid actions
-Non-genomic steroid actions
Intracellular receptors that regulate gene transcription
Membrane-bound receptors (PMIDs)
In what fashion is GnRH released? What hormones does it regulate?
GnRH is released in a Pulsatile way.
GnRH regulates Gonadotropin hormones: LH & FSH
What would happen if GnRH were released in a non-pulsatile way?
LH and FSH secretion would attenuate
How do pituitary gonadotrophs mediate effects of GnRH?
Through second messengers:
What are the Gonadotropins? What are they made of and what does each part do?
LH & FSH
They are glycoproteins made of:
-a-subunit => ...
-B-subunit => hormone specificity
-Carbohydrate moiety => determines circulation half-life
Which has a shorter circulation half-life?
LH = 20 min
FSH = 120 min
What characterizes FSH isoforms with high biological activity?
-Sialic acid (small amounts)
How is prolactin regulated? What does it do? What other hormone does it work in synergy with? What is the result of a prolactin-producing tumor? How can it be treated?
Prolactin-inhibiting factor = Dopamine
Prolactin binds to Leydig or Theca cells & facilitates LH-stimulated secretion of gonadal steriods.
Impotency. This can be fixed by:
-Bromoergocryptine (Dopamine agonist)
-surgical removal of tumor
What is inhibin? What does inhibin do? What produces it?
It suppresses synthesis and secretion of FSH
-Sertoli & Granulosa cells
What does activin do? What is unique about its structure?
Stimulates FSH release
Has 2 Inhibin B-subunits
What are the four Endocrine Stages of Sexual Maturation and what is unique about them?
1) Sexual differentiation
-high LH & FSH levels independent of GnRH secretion
2) Immature Quiescence
-reduced hypothalamic GnRH release
-increased sensitivity to gonadal steroid feedback
Both of these cause Gonadotropin (LH & FSH) insufficiency
3) Phenotype of Puberty
-Spermatozoa appear in epididymis
-testicle size increases
-somatic changes reflecting internal changes (spermatogenesis & androgen production)
Boys reach a maximum height growth of 10cm/year by age 11.
defined as (depends on species)...
Girls reach a maximum height growth of 9cm/year by age 10.
4) Endocrinology of Puberty
-increased GnRH release & Gonadotropin secretion => gonadal steroid production => increased osteoblast activity & eventually the close of epiphyseal plates
-Increased Gonadotropin pulse Amplitude (NOT frequency)
-increased serum Insulin-like Growth Factor I (metabolic signal to facilitate the onset of puberty)
-stimulated by increase secretion of estrogens
-hypertrophy comes from increased fat deposition and areola growth
-happens about 2 years before puberty
-DHEA & delta-4-androstenedione increase, causing development of auxiliary and pubic hair
-regulated independently of the hypothalamic-adrenal axis
-may be GnRH-dependent or -independent
-Central Precocious Puberty (GnRH-dependent) is treated by long-acting GnRH agonist or specific GnRH antagonist so the pituitary will be desensitized and gonadotropin secretion will be suppressed
-it is a polygenic condition
During puberty, which aspect of Gonadotropin pulse changes the most?
What metabolic signal facilitates the onset of puberty?
Insulin-like Growth Factor I (IGF I)
What is Thelarche? What causes it? When does it happen?
Increased secretion of estrogens at the start of puberty
Hypertrophy comes from:
-increased fat deposition
What is Adrenarch? When does it happen? How is it regulated?
...contribute to development of auxiliary and pubic hair
It is REGULATED INDEPENDENTLY of the hypothalamic-adrenal axis
What is precocious puberty? how many genes are involved?
Is Central Precocious Puberty:
How can CPP be treated?
Premature sexual development
Multiple. It is Polygenic.
CPP is GnRH-dependent.
CPP can be treated with:
-long-acting GnRH agonist
-specific GnRH antagonist
...to desensitize the pituitary and suppress gonadotropin secretion
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