Hypothalamus and Pituitary Flashcards by Morgan McLuckey

The posterior pituitary is composed of neural tissue because _______.

It is an outgrowth of the hypothalamus. Hypothalamic neurons end is the pos. pituitary. The upper portion is called the median eminence.

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Which nuclei secrete into the posterior lobe?

Paraventricular and supraoptic (oxytocin and vasopressin)

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What does the anterior pituitary produce?

FSH, LH, ACTH, TSH, prolactin, GH (flat PG)

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Anterior pituitary releasing factors travel to the adenohypophysis via…

hypophyseal-portal circulation

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CRH…

stimulates ACTH

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TRH…

stimulates TSH and prolactin

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GHRH…

simulates GH

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Somatostatin…

inhibits GH

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GnRH…

stimulates LH and FSH

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Prolactin inhibiting hormone (dopamine)…

….inhibits PRL (shocker)

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Describe GH control (briefly)

Stimulated by GHRH and inhibited by somatostatin

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What are neurotransmitter systems that stimulate GHRH and/or inhibit somatostatin?

Catecholamines (alpha2-adrenergic)
Dopamine (D1 or D2)
Excitatory amino acids (NMDA and non-NMDA receptors)

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What neurotransmitter systems inhibit GHRH and stimulate somatostatin?

beta-adrenergic

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During fasting, GH…

antagonizes insulin action, helps mediate glucose-sparing (stimulate gluconeogenesis)

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During anabolic or absorptive phase, GH…

facilitates insulin action to promote growth

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In protein intake:
In carbohydrate intake:
In fasting:

GH up and insulin up
GH down and insulin up
GH up and insulin down

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What is gigantism?

Excess GH (eosinophilic adenoma of somatotrophs) during early life
- symmetrical enlargement, overgrowth of long bones, connective tissue, visceral organs

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What is acromegaly?

Excess GH after body growth has stopped

- Overgrowth of cancellous bones, protruding jaw, thickening of phalanges, overgrowth of visceral organs

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Proteolytic processing of prepro-opiomelanocortin (POMC) makes…

ACTH, beta and gamma lipotropin, beta-endorphin, alpha-melanocyte-stimulating hormone (alpha-MSH)

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What can overproduction of ACTH darken the skin?

alpha-MSH (a co-product) stimulates melanocytes

Also antipyretic and anti-inflammatory effects (inhibit CRH and LHRH too)

ACTH regulates…

adrenal cortex and synthesis of adrenocorticosteroids

What is Addison’s Disease?

Lack cortisol from zona fasciculata; lack negative feedback to suppress ACTH

Skin color will darken

What is beta-endorphin?

Co-product of ACTH synthesis; binds to opiate receptors; “runner’s high”

What stimulates ACTH secretion?

CRH, ADH, stress, hypoglycemia

Deficiency of ADH (vasopressin, is diabetes insipidus) is accompanied by...

decrease in ACTH release

ACTH has a ____ pattern of release.

circadian; higher in the morning and dependent on sleep-wake cycle Opposes circadian pattern of GH secretion

Lack of cortisol negative feedback leads to high ACTH and other adrenal corticosteroids, such as...

adrenal androgens Adrenogenital Syndrome: masculinization of female fetus

What are glycoprotein hormones?

LH, FSH, TSH, hCG all alpha subunits are identical, but their beta subunits offer specificity

LH release is stimulated by... | FSH secreted is inhibited by...

``` GnRH Inhibin (produced by testes and ovaries) ``` Pulsatile release of these causes distinct LH and FSH patterns

Female LH is _____ and male LH is ______

cyclic (surge at ovulation); constant

______ disappears in menopause

inhibin

Testosterone synthesis in the Leydig cells is stimulated by:

LH Feedback inhibits GnRH production in hypothalamus

What does progesterone do?

Suppresses ovulation (oral contraceptives)

What inhibit GnRH release?

Dopamine, endorphin, prolactin

Overproduction of prolactin can cause...

amenorrhea (shuts off GnRH) - treat with bromocryptine, a dopamine agonist, or removal of pituitary tumor Prolactin inhibition affords post-partum contraceptive effect

Estradiol a high plasma concentrations in late follicular phase of ovarian cycle...

stimulates GnRH and LH surge to trigger ovulation

TSH is synthesized in thyrotrophs of ant. pituitary and is relatively steady. It acts on the thryroid. Negative feedback is accomplished by _____

What is Grave's Disease?

Hyperthyroidism caused by circulating antibodies to the TSH receptor; mimic action of TSH --> elevated thyroid hormones (goiter)

Prolactin is produced by ______

lactotrophs Prolactin required for lactogenesis and breast development; stimulated T cell functions

Prolacin is the only anterior pituitary hormone that is _______

tonically inhibited (under influence of many factors; balance favors inhibition)

Dopamine _____ prolactin

inhibits

Prolactin releasing hormone is ____

TRH - also, oxytocin - synthesis enhanced by estradiol

PRL can be elevated by...

lesions that interfere with portal blood flow to anterior pituitary

ADH synthesized by: | Oxytocin synthesized by:

supraoptic nucleus paraventricular nucleus posterior pituitary; as preprohormones; released via an action potential from hypothalamus

Oxytocin stimulates _______

Myoepithelial contractions (uterus during parturition; mammary gland during lactation)

______ is a major stimulus for oxytocin release.

Suckling Sensory receptors in nipple

Increased oxytocin in plasma during...

ovulation, parturition, coitus

Estrogen _____ oxytocin synthesis and ______ threshold for release

increases; lowers