Endocrine System Physiology 1 - Teel

Question 1

2 Hormones secreted by pituitary gland:

Answer 1

AVP

Oxytocin

Question 2

Regulatory factors of Hypothalamic releasing hormones

___ stimulates secretion of ___

Answer 2

CRH (corticotropin) : ACTH, also stimulates expression of POMC gene
TRH (thyrotropin): TSH / PRL
GHRH (Growth hormone) : HGH
GnRH (Gonadotropin) : Stimulates secretion of FSH and LH

Question 3

Regulatory factors of Hypothalamic releasing hormones

____ inhibits secretion of ____

Answer 3

Somatostatin: GH TSH
Dopamine: PRL

Question 4

Hormones of Anterior Pituitary

ACTH (Adrenocorticotropic hormone)

Answer 4

Regulates function of adrenal cortex
Derived from POMC
Regulated by CRH
Related to stress
Glucocorticoids inhibit ACTH synthesis / secretion
Diurnal rhythm exists

Question 5

Hormones of Anterior Pituitary

TSH (Thyroid-stimulating hormone)

Answer 5

Regulates function of thyroid gland
TRH regulates synthesis / secretion of TSH
Exhibits diurnal variation, stimulated by cold temps
Negative feedback regulation by thyroid hormones

Question 6

Hormones of Anterior Pituitary

HGH (Human growth hormone)

Answer 6

Regulates growth in childhood
Stimulates secretion of insulin-like growth factor 1 (IGF-1)
Displays pulsatile secretory pattern with peaks during sleep

Question 7

Hormones of Anterior Pituitary

Gonadotropic hormones

Answer 7

LH (Luteinizing hormones)
FSH (Follicle-stimulating hormone)

Both regulate testes / ovaries
Both regulated by GnRH (Gonadotropin-releasing hormone)

Question 8

Hormones of Anterior Pituitary

Prolactin

Answer 8

Regulates synthesis of milk of the breast

Question 9

Significance of Somatotrophs

Answer 9

In anterior pituitary, these synthesize prohormone that is converted to HGH
Stored in little granules

Question 10

What influences growth hormone?

Answer 10

Blood glucose levels. You can have peaks of growth hormone during day depending on your blood glucose levels.

Question 11

Somatotroph mechanism

Answer 11

GHRH from hypothalamus stimulate somatotrophs in anterior pituitary to make HGH.

Somatostatin also produced here

Contains both GHRH receptor and SS receptor. Secondary messengers are needed (cAMP)

Question 12

Metabolic Effects of HGH

Answer 12

Skeletal muscle increases in glucose production, but decreases glucose uptake from adipose tissue. Decreasing uptake means there’s more glucose in blood. So basically less glucose in skeletal muscle

Adipose tissue: increased lipolysis
Liver (hepatocytes): increased gluconeogenesis (making glucose)

All of these effects have an insulin resistant reaction. These are all insulin antagonists

Question 13

Importance of IGF with HGH

Answer 13

Growth promoting actions of growth hormone (HGH) have to include IGF 1 and 2, particularly 1.

Question 14

Mechanisms of IGF-1

Answer 14

binds to proteins synthesized by liver
levels in plasma are fairly stable
acts through specific receptor
begins to regulate growth by age 3-4

Note: IGF-2 has similar actions to IGF-1, but has less dependence on HGH.

Question 15

Stages of Growth

In utero:

Answer 15

Important things:
IGF-II, placental lactogen, fetal insulin, cortisol, T4 and nutritional factors

Question 16

Stages of Growth

In early childhood:

Answer 16

HGH, IGF-1, cortisol, insulin, T4, nutritional factors

Question 17

Stages of Growth

Puberty:

Answer 17

HGH, IGF-1, cortisol, insulin, T4, gonadal steroids, nutritional factors

Question 18

Mechanism of production of T3/T4

Answer 18

TRH released from hypothalamus, traveling down blood supply to thyrotrophs (cell in anterior pituitary), producing TSH

TSH released into circulation, travels to thyroid gland.

Thyroid responds to TSH by producing T3 / T4

Question 19

Thyrotroph mechanism

Answer 19

Contain TRH receptors. Secondary messenger mediated. Release TSH

Question 20

Follicular Cell

Answer 20

functional part of the thyroid gland. Absolutely dependent on dietary iodine.
TSH receptor in basolateral side.

Question 21

Thyroid follicular cell and glandular function

mechanism

Answer 21

Iodine / Na+ from blood cotransported via basolateral membrane of follicular cell. I- then goes into lumen converting into I2

Thyroglobulin (TG) synthesized within thyroid follicular epithelial cell, then gets transported into lumen.

In follicular lumen, TG links up with Iodine, forming either MIT and DIT (moniodotyrosine, diiodotyrosine)

TG reassembles MIT and DIT to form either T3 or T4 (still attached to TG).

T3 / T4 attached to TG from colloid now travels back into follicle cell

T3 / T4 cleaved inside cell, then travel out of cell on basolateral side

Question 22

Mechanism after T3/T4 transported out of follicle cell

Answer 22

Binds to Thyroid-binding globulin (TBG) / albumin

Question 23

Actions of Thyroid hormones

Answer 23

T4 converts to T3. T3 binds to thyroid hormone receptor which is linked to retinoid X receptor in target cells.

Binding affects alteration of gene transcription and synthesis of proteins that initiate action of thyroid hormones.

Tons of effects, mainly metabolism effects. Same with cardiovascular. Upregulates a bunch of stuff.

Question 24

Thyroid gland dysfunction

Hyperthyroidism

Disease associated with this

Answer 24

moist skin, palpitations, arrythmias, murmurs of heart, CHF, decreased VC / lung compliance, Diarrhea, nervousness, neutropenia, splenomegaly

upregulate gluconeogenesis / glycogenolysis / more

Gain too much stuff

Example: Grave’s Disease. Antibodies bind to and stimulate TSH receptors.

Question 25

Thyroid Gland dysfunction

Hypothyroidism

Disease associated with this

Answer 25

dry skin, bradycardia (heart rate too slow), slow reflexes, hypoventilation, gain weight,

downregulate gluconeogenesis / glycogenolysis / more

Lose a lot of stuff

Example: Hashimoto’s disease. TSH blocking antibodies.