endocrinology lecture 1 and 2

Question 1

What does endocrine signaling involve?
What is an important endocrine gland, what is an example of their target site?

Answer 1

-involves hormone secretion into the blood by an endocrine gland
-anterior pituitary gland releases LH and FSH (follicle stimulating hormone) into the blood which transports to gonads (cells of ovary and testes)
-gonads produce steroid hormones, estrogen (female) and androgens (male)

Question 2

Where does neuroendocrine stimulus usually go, what is the source?
-what can dopamine be?

Answer 2

-source of hormones are nerve cells
-stimulus goes to hypothalmus, then anterior pituitary
-dopamine can be a neurotrasmitter or hormone

Question 3

paracrine signaling vs autocrine signaling?

Answer 3

-paracrine signaling is when cell releases a signaling substance to a nearby cell
-autocrine is when the cell is talking to itself, it releases hormones and also expresses receptor on its own cell

Question 4

What are the 6 steps of communication by hormones?

Answer 4

1. synthesis
2. release of hormone
3. transport to target site by bloodstream
4. detection
5. change in cellular metabolism
6. removal of hormone

Question 5

Where does hypothalmic pituitary signaling occur?
Where does it go from?

Answer 5

-via blood vessels of the pituitary stalk
-from hypothalmus to anterior pituitary, hypothalamic neurohormones either inhibit of activate one of the 6 type of hormone producing cells in anterior pituitary

Question 6

What are protein hormones produced by?
Where does synthesis of the proteins occur?
What does the rough ER do?
What does golgi apparatus do?
What do vesicles do?

Answer 6

pre-pro proteins
-on ribosomes, prepro hormones
-turns prepro hormones into prohormones
-golgi packages prehormone into hormone and other peptides
-vesicles do storage of hormone

Question 7

What are the main steroids?

Answer 7

Cortisol, aldosterone, testosterone, and estradiol
-also vitamin D and progesterone

Question 8

What are the 3 thyroid hormones?
What are the levels of each hormone?
What is different about the third one?

Answer 8

T4 (90%) and T3 (9%) which are thyroid hormones, and rT3 (0.9%) which does not bind to thyroid hormones

Question 9

What is special about the mechanism of the hormone receptor?
how can the receptors be regulated?

Answer 9

-it has a lock and key mechanism, which means the hormone has a structure complementary to receptor
-can be regulated by increasing or decreasing the hormone activity and/or synthesis

Question 10

What are 3 mechanisms by which a hormone can exert effects on target cells?

Answer 10

1. direct effects on function at the cell membrane
2. intracellular effects mediated by 2nd messenger systems
3. intracellular effects mediated by genomic or nuclear action

Question 11

What is example of direct effect vs 2nd messenger system and genomic/nuclear action of hormones?

Answer 11

1. direct effect- a target binds to receptor
   2.you have a first messenger than binds to receptor then an inactive protein turns into an active protein leading to a biological effect
2. genomic signaling is by nuclear receptors which include receptors for steroid hormones, leading to an altered functional response

Question 12

What is the feedback mechansim for hormone secretion?
What is an example?

Answer 12

-it is negative feedback mechanism
Ex. Ca++ acts in negative feedback loop to regulate plasma calcium levels

Question 13

What are the 2 different tissues in the pituitary gland?

Answer 13

1. anterior pituitary is endocrine tissue
   2.posterior pituitary is neuronal tissue

Question 14

Anterior pituitary hormones from hypothalmus:
What does GnRH release (gonadotropin releasing hormone)?
What does GHRH release?
What does somatostatin release?
What does TRH release (thyrotropin releasing hormone)
What does cortiocotropin releasing hormone release (CRH)?

Answer 14

-FSH and LH which fo to gonads
-growth hormone which goes to live and other organs
-growth hormone and TSH (thyroid stimulating hormone)
-TSH (thryoid) and prolactin (breasts)
-ACTH which goes to adrenal cortex (adrenocortiotropin hormone)

Question 15

What are the posterior pituitary hormones?
What are their circulating half lives?
What do the supraoptic nucleus and paraventricular nucleus produce respectively?

Answer 15

-arginine vasopressin and oxytocin which control smooth muscle
tone
-1-3 minutes
-vasopressin (or ADH) and oxytocin

Question 16

What are the anterior pituitary targeting hormones?
Which hormone is not produced by pre-pro peptide?

Answer 16

-TRH, GnRH, somatostatin, GRH, PIH, and CRH
-PIH (prolactin inhbitng hormone) is not gene encoded, it is a derivative of free tyrosine

Question 17

What is oxytocin responsible for in the body in females?

Answer 17

child birth-causes uterine contraction
milk ejection
behavioral effects-reduces anxioty and enhances bonding

Question 18

what does oxytocin do in the body for males?

Answer 18

-ejaculation
-behavioral effects-reduces anxiety and enchances bonding

Question 19

What components are in the thyroid gland?
What is the synthesis under the control of?
In what gender is it larger in, what amount is needed for healthy thyroid state?

Answer 19

thyroglobin which contaisn hormones T4 and T3
-under the control of TSH of pituitary gland
-larger in females than males
-need 3g to maintain healthy state

Question 20

How are thyroid cells able to trap iodide/transport it?

Answer 20

thyroid follicular cells are able to trap iodide and transport it across the cells against the chemical gradient (active transport)

Question 21

How does iodine help form thyroid hormones T4 and T3?
What regulated formation of T3 and T4

Answer 21

-iodine is used for iodination of tyrosine residue of thyroglobulin to form monoiodotyrosine (MIT) and diiodotyrosine (DIT)
-for T4 coupling of 2 DIT form T4 while coupling of one MIT which one DIT forms T3
-formation is increased by TSH

Question 22

What regulates synthesis + control of TSH?
What happens when T3 and T4 levels increase/
What receptors does TSH interact with/

Answer 22

TRH controls that (thyrotropin releasing hormone)
-they exert negative feedback on hypothalamic and pituitary levels to decrease release of TRH and TSH
-interacts with specific receptors located on follicular cells, leading to increased production of T4 and T3

Question 23

What happens to T3 and T4 if iodine supply is deficient?
What can stimulation of thyroid cells lead to?

Answer 23

-the synthesis of T3 and T4 decreases which causes TSH production to increase and thyroid follicular cells to be constantly stimulated
-can lead to a goiter

Question 24

What is it called when a thyroid is unable to synthesize active thyroid hormones due to iodine defiency?

Answer 24

-non toxic goiter (doesnt produce thyroid hormones no matter how large it is)

Question 25

What does increase thyroid hormone release do to calorigenesis in most cells, like cardiac output, oxygenation, and rate of breathing?

Answer 25

-it increases all of those thing by increasing rate and strength of contractions, increase oxygenation in blood, increase number of RBC in circulation

Question 26

How does increased thyroid effect carb metabolism? -effect on lipid turnover?

Answer 26

-promtes glycogen formation in liver, and increased glucose uptake in adipose tissue+muscle -increased lipid synthesis, increased lipid metabolizaition, increased lipid oxidation

Question 27

How does thyroid hormne effect protein metabolism and growth?

Answer 27

-Stimulates protein synthesis -promotes neural branching and myelination of nerves -promotes development and muturation of nervous system -stimulates GH secretion, bone growth, and liver IGF-I production

Question 28

What increases Basal metabolic rate (BMR)?

Answer 28

-T4 and T3 since they have effect on carbs, lipids, and proteins, which increases need for O2

Question 29

How does thyroid effect CNS?

Answer 29

-required for normal brain development, and for synthesis of nerve growth factor

Question 30

Which actions of thyroid hormone are dependent and independet of protein synthesis?

Answer 30

-T3 and T4 entering target nucleus to bind to cognate receptor and alter transcription of genes is dependent on synthesis of protein -hormones inducing interaction with plasma membrane and mitochondira is independent of protein synthesis, not blocked by inhibitors -T3/T4 increasing uptake of amino acids at plasma membrane is independent of protein synthesis

Question 31

What is too much or too little thryoid hormone called?

Answer 31

-too little=hypothyroidism ( low levels of thyroid hormones) -too much-hyperthyroidism (high levels of thyroid hormones)

Question 32

What are the 4 types of hypothyroidism?

Answer 32

1. primary hypothyroidism (inability to synthesize active thyroid hormone) 2.secondary hypothyroidism (at level of pituitary, little stimulation of TSH) 3. tertiary hypothroidism (at level of hypothalamus, little to no synthesis of TRH (thyrotropin releasing hormone) 4. infantile hypothyroidism (absence of thyroid gland at birth

Question 33

What is primary hypothyroidism caused by?

Answer 33

-atrophy of thyroid -autoimmune thyroiditis-destruction of anitbodies against cellular components of thyroid (hashimotos disease) -goiterois hypothyroidism (block of T3 and T4 synthesis)

Question 34

What can infantile hypothyroidism lead to?

Answer 34

-decreased growth and mental development, can develop dwarfism or cretinism (mental retardation)

Question 35

What are the 3 types of hyperthyroidism?

Answer 35

1. primary hyperthyroidism-at level of thyroid gland 2.secondary hyperthyroidism- at level of anterior pituitary gland, no negative feedback from increased T3/T4 levels to synthesize TSH 3.tertiary hyperthyroidism- at level of hypothalamus- no negative feedback of high T3/T4 to decrease synthesis of thyrotropin releasing hormone (TRH)

Question 36

What are the causes of hyperthyroidism, what does constant stimulation lead to in primary thyroidism?

Answer 36

1. toxic diffuse goiter, graves disease which is an autoimmune disease characterized by LATS (long acting thyroid stimulator), mimics T3 and T4 action -constant stimulation of LATS causes a goiter to create a toxic goiter 2.thyroid cancer-synthesizing thyroid hormone independent of TSH

Question 37

What are treatments for hyperthyroidism?

Answer 37

1. can do surgery +replacment therapy 2.adminitration of radioactive iodide (destroys thyroid follicles) 3.antithyroid drug like propylthiouracil (blocks addition of iodine to thyroiglobulin)