168. Hypothalamic-Pituitary Basic Physiology

Question 1

Confers the biologic specificity of hormones

Answer 1

beta-subunit

Question 2

Essential for boney growth and has effects on fat, muscle, and CHO GHRH (+) and somatostatin (-)

Answer 2

Growth hormone

Question 3

High estrogen levels of pregnancy result in hyperplasia of lactotrophs and high ___ levels

Answer 3

Prolactin

Question 4

Stimulates gonadal steroid production

Midcycle surge triggers ovulation (release of egg) GnRH (+)

Answer 4

LH

Question 5

Derive from an evagination of neural ectoderm of the ventral diencephalon

Answer 5

Posterior lobe of pituitary

Question 6

Stimulates mild let-down and postpartum uterine contraction

Stimulated by suckling

Answer 6

Oxytocin

Question 7

Mutations in these peptides give rise to combined pituitary hormone deficiency through lack of development of certain pituitary cells but hypothalamic structures are normal

Answer 7

Pit-1 and PROP-1

Question 8

Stimulates follicle and sperm development GnRH (+)

Answer 8

FSH

Question 9

Under tonic inhibition by the hypothalamus via dopamine

Cutting of the stalk causes hypopituitarism but also an increase in this hormone

Answer 9

Prolactin

Question 10

Secreted by the somatotrophs (50% of pituitary cells)

Promotions of linear growth at the growth plates of bones

Increases osteoclast differentiation and activity

Increases osteoblast activity

Increases bone mass by endochondral bone formation

Answer 10

Growth hormone

Question 11

Converts electrical signals from the retina into hormonal signals

Answer 11

Pineal gland

Question 12

Need ___ secretion instead of continuous for adequate hormone release

Answer 12

Pulsatile

Question 13

Localized in hypothalamic nuclei that project to the median eminence to secrete peptide and bioamine releasing and inhibiting hormones into the proximal end of the hypothalamic-pituitary portal vessels

Answer 13

Hypophysiotropic neurons

Question 14

Made by Liver and bones after Growth Hormone has acted on them

• most comes from liver

Then acts in a negative feedback loop on the pituitary and hypothalamus

Answer 14

IGF-1

Question 15

Primary regulator of ADH secretion

Senses hyperosmolality (hypernatremia) which stimulates ADH release

Senses hypoosmolality (hyponatremia) which suppresses ADH release

Answer 15

Osmoreceptors in hypothalamus

Question 16

Produced by corticotrophs (10-20% of pituitary cells)

Derived from POMC

Main product in pituitary

Stimulates adrenal cortex to produce cortisol and adrenal androgens

Little effect on aldosterone

Stimulated by CRH Stress mediated

Answer 16

ACTH

Question 17

Secreted by pituitary lactotrophs (15% of pituitary cells)

Stimulates breast epithelium to proliferate

• in conjunction w/ estrogen, progesterone, thyroid hormone, cortisol, and insulin

Induces milk production in the puerperium

Dopamine-receptor blockers can increase levels of this hormone

Suckling is the normal stimulus for secretion in the puerperium

Answer 17

Prolactin

Question 18

Produced by gonadotrophs (10-15% of pituitary cells)

In ovary, binds to receptors on theca cells where it stimulates the production of androgens and steroid precursors that are transported to granulosa cells for aromatization to estrogen

In testes, binds to receptors on Leydig cells where it stimulates testosterone production

Triggers ovulation if properly timed

Answer 18

LH

Question 19

Primary regulation of aldosterone is performed by ___ along with from the adrenal gland after ACTH stimulation

Answer 19

Renin-Angiotensin System

Question 20

Provide negative feedback at both the pituitary and hypothalamic levels with decreases in TRH and increases in somatostatin

Answer 20

T4 and T3

Question 21

Originate in the supraoptic and paraventricular nuclei

Traverse the pituitary stalk

Release vasopressin and oxytocin from nerve endings in the posterior pituitary

Answer 21

Neurohypophysial neurons

Question 22

Main androgen responsible for closing of epiphyseal growth plates

Answer 22

Estrogen

Question 23

Derives from Rathke’s pouch

Answer 23

Anterior lobe of pituitary

Question 24

TRH, VIP, and maybe other peptides release ___ in the setting of low dopamine

Answer 24

Prolactin

Question 25

Synthesized in magnocellular neurons in the supraoptic and paraventricular nuclei of the hypothalamus Acts by binding V2 receptors in renal collecting ducts making them more water permeable - activation of aquaporin 2 channels Primary action it to maintain normal serum osmolality through water reabsorption Also acts on V1 receptors on vascular smooth muscle to cause muscle contraction and an increase in BP

Answer 25

ADH (vasopressin)

Question 26

From sertoli cells and ovarian granulosa cells that feeds back to inhibit FSH release Acts on pituitary gland to inhibit FSH and LH secretion

Answer 26

Inhibin

Question 27

Controlled only by water balance - controlled by vasopressin and thirst

Answer 27

Serum osmolality

Question 28

Produced by the thyrotrophs (5% of pituitary cells) Glycoprotein with an alpha and beta subunit Stimulates all aspects of thyroid function as well as thyroid gland growth

Answer 28

TSH (Thyrotrophin)

Question 29

Stimulates amino acid uptake into tissue and increases muscle Promotes lipolysis with fat breakdown Causes resistance to the action of insulin (a counter-regulatory hormone)

Answer 29

Growth Hormone

Question 30

Stimulates thyroid hormone production and thyroid growth TRH (+) and somatostatin (-)

Answer 30

Thyrotropin (TSH)

Question 31

Linear growth is dependent on the stimulation of this protein from the liver and locally in other tissues, such as the epiphyseal growth plate Measure this when wanting to assess GH status

Answer 31

IGF-1

Question 32

Can override osmotic regulation in extreme conditions - 10-15% blood volume or pressure drop to override the osmolality control

Answer 32

Baroreceptors (volume receptors) in chest

Question 33

Influences hormone cycles in humans more than light-dark

Answer 33

Sleep-wake cycles

Question 34

Common to TSH, LH, FSH, and chorionic gonadotrophin

Answer 34

alpha-subunit

Question 35

Act as carriers of IGF in plasma Prolong the half-life of IGF in circulation Regulate IGF access to receptor in extracellular fluid

Answer 35

IGFBPs (IGF binding proteins)

Question 36

Binds to receptors in the breast, causing contraction of myoepithelial cells around the alveoli and ductules to eject milk Suckling stimulates tactile receptors, sending signal to hypothalamus to release \_\_ Released during vaginal stretching with delivery of infant and is important in causing uterine contraction then to prevent blood loss

Answer 36

Oxytocin

Question 37

Hyperglycemia suppresses __ secretion

Answer 37

Growth hormone

Question 38

Produced by gonadotrophs (10-15% of pituitary cells) In **ovary**, binds to receptors on _granulosa cells_ where it induces enzymes that are involved in estrogen synthesis and promotes follicle growth In **testes**, binds to receptors on _Sertoli cells_ where it stimulates spermatogenesis and inhibin-related proteins

Answer 38

FSH

Question 39

Stimulates water reabsorption in the kidney collecting duct Stimulated by hyperosmolality and intravascular volume/pressure loss

Answer 39

Vasopressin

Question 40

Stimulates cortisol and adrenal androgen production and adrenal growth Strong diurnal rhythm CRH (+) and vasopressin (+)

Answer 40

ACTH