Male Reproductive Endocrinology Flashcards

1
Q

Axons of GnRH neurons

A

Extend into pituitary stalk and terminate on hypothalamic-hypophyseal portal system (capillary network) into which they release GnRH

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2
Q

Portal system

A

Blood from capillaries of one organ is transported to capillaries of another organ by a connecting vein or veins (returns to systemic circulation instead of pulmonary)

-allows small quantities of releasing hormones to act on anterior pituitary before dilution through general circulation

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3
Q

What pattern do GnRH hormones secrete GnRH?

A

An episodic pattern

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4
Q

How is GnRH captured?

A

Captured in primary portal plexus (PPP) and transferred to anterior pituitary through portal veins into secondary portal plexus (SPP)

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5
Q

Posterior pituitary

A

Does not have a portal system, axons of paraventricular nucleus (in hypothalamus) extend into posterior pituitary and hormones are captured directly by capillaries

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6
Q

Do GnRH hormones have receptors?

A

GnRH neurons lack receptors for testosterone and estradiol so negative feedback is indirect through presynaptic steroid-sensitive neurons

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7
Q

Release of GnRH

A

Pulsatile and waves of FSH, then LH, then testosterone follow

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8
Q

What does FSH act on?

A

Sertoli cells which release inhibin and provide negative feedback to anterior pituitary to directly suppress FSH release

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9
Q

What does LH act on?

A

Leydig cells which release testosterone that provides negative feedback to GnRH neurons in hypothalamus

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10
Q

Testosterone feedback/diffusion

A

Through blood, or diffuses across basement membrane to sertoli cells where it is converted to dihydrotestosterone (DHT) and/or E2 which feedbacks to hypothalamus reducing GnRH production

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