Endocrine Lecture II

Question 1

Describe the location, structure, and function of the pituitary gland.

Answer 1

small gland inside sella turcica, connected to hypothalamus via infundibulum

Question 2

List and describe the effects of the six hormones released by the anterior pituitary gland.

Answer 2

all tropic, AA-based, cyclic AMP except growth hormone

growth hormone: stimulate growth, direct actions are metabolic/anti-insulin, indirect effects are growth promoting

thyroid stimulating hormone: stimulate normal development and secretory activity of thyroid

adrenocorticotropic hormone: stimulates adrenal cortex to release corticosteroids

FSH: gonadotropin that stimulates gamete production

LH: gonadotropin that triggers ovulation and stimulates estrogen/progesterone/testosterone

prolactin: stimulates milk production

Question 3

describe the hypothalamic-pituitary axis

Answer 3

description of the relationship between the hypothalamus and pituitary gland

Question 4

Explain the structural and functional relationships between the hypothalamus and the pituitary gland, including…
the hypothalamic-hypophyseal tract

Answer 4

hormones travel from the hypothalamus down the hypothalamic-hypophyseal tract, which is a group of axons inside the infundibulum leading to the posterior pituitary gland, and ADH and oxytocin are stored at the axon terminals in the posterior pituitary. When APs fire and travel down the hypothalamic-hypophyseal tract, ADH/oxytocin are released into blood

Question 5

Explain the structural and functional relationships between the hypothalamus and the pituitary gland, including… the role of the hypophyseal portal system and plexuses

Answer 5

neurons put releasing/inhibiting hormones from hypothalamus into primary capillary plexus → hypophyseal portal veins → larger secondary plexus → hormones leave blood there and bind to receptors on the anterior pituitary gland

Question 6

List and describe the effects of the various releasing and inhibiting hormones that are secreted by the hypothalamus.

Answer 6

growth hormone, thyroid hormone, corticosteroids, gonadal hormones feed back to inhibit more release

GHRH and GHIH control growth hormone

TRH, GHIH and thyroid hormones control TSH

CRH and corticosteroids control adrenocorticotropic hormone

GnRH and gonadal hormones control gonadotropins (FSH & LH)

PIH controls prolactin (see dedicated slide)

Question 7

What regulates prolactin?

Answer 7

PIH (dopamine) inhibits release until needed, so decreasing PIH leads to lactation

High levels of estrogen also contribute to milk production

Suckling → increased milk production (positive feedback)

prolactin and estrogen both increase during pregnancy

Question 8

List and describe the effects of the two hormones released by the posterior pituitary gland.

Answer 8

ADH-anti-diuretic b/c kidney tubule inserts more aquaporins, more H20 reabsorption

oxytocin-uterine contractions, milk ejection

Question 9

Explain several homeostatic imbalances resulting from the hyposecretion or hypersecretion of pituitary hormones.

Answer 9

hyposecretion of ADH (posterior) - diabetes insipidus - decreased secretion of ADH (central) or kidney resistance to ADH (nephrogenic)

Question 10

Describe the location, structure, and function of the thyroid gland.

Answer 10

anterior neck on the trachea, just inferior to larynx, isthmus + two lateral lobes, lobes have follicles - hollow spheres of follicular cells, colloid/thyroid hormone in middle of follicles = thyroglobulin + iodine, parafollicular cells produce calcetonin (decrease blood Ca2+)

Question 11

List and describe the three hormones (two groups) that are secreted by the thyroid gland.

Answer 11

thyroid hormone affects almost all cells, works with growth hormone, major metabolic hormone, 2 forms act on same receptors, T3 is more potent, T4 may be more stable and is more abundant, converted to T3 at tissue level,

thyroid → think metabolism

• increase basal metabolic rate and heat production (calorigenic effect)
• regulate tissue growth and development - hand in hand with GH - development and repro abilities
• maintain blood pressure (increases/upregulates adrenergic receptors that bind E & NE → more vasoconstriction → maintained pressure in blood vessels)

Question 12

Describe the synthesis and release of thyroxine.

Answer 12

hypothalamus secretes TRH → anterior pituitary secretes TSH → thyroid gland releases thyroid hormones thyroxine (T4) and triiodothyronine (T3) → target cells -> T4 is more stable, but it’s converted to T3 at some tissues because T3 more potent

negative feedback from TSH and thyroid hormones

Question 13

Explain the homeostatic imbalances resulting from the hyposecretion or hypersecretion of thyroid hormone including Graves disease

Answer 13

Graves - body produces antibodies against thyroid follicular cells, mimic effects of TSH → stimulate release of thyroid hormone from thyroid gland → hypersecretion → increased basal metabolic rate, increased body temp and sweating, irregular heartbeat or rhythm, nervousness, jitteriness, decreased body weight, bulging eyes from tissue buildup behind eyes

treatment = surgical removal of thyroid, destroy thyroid by radioactive iodine

Question 14

Describe the location, structure, and function of the parathyroid gland.

Answer 14

4-8 small yellow-brown glands embedded in posterior aspect of thyroid gland, release PTH

Question 15

Explain the functions of parathyroid hormone throughout the body.

Answer 15

released in response to low blood Ca2+, targets osteoclasts, increases Ca2+ absorption at DCT of kidneys, also increases kidney’s activation of Vitamin D to improve absorption of Ca2+ in intestines

Question 16

Describe the location & basic structure of adrenal gland

Answer 16

sit on top of each kidney like hats, two different glands - cortex and medulla, cortex is more superficial has three layers and medulla is deeper and composed of nervous tissue (“misplaced sympathetic ganglion”)

Question 17

Differentiate the three regions of the adrenal cortex, state the class of hormones produced by each, and identify the chief hormone of each class.

Answer 17

zona glomerulosa-smallest layer - mineralocorticoids regulate [electrolyte] incl. Na+ and K+, aldosterone is most important here

zona fasciculata-largest layer-glucocorticoids-cortisol

zona reticularis-gonadocorticoids-closest to medulla-androgens (precursor of testosterone)

24 known hormones

Question 18

Describe the physiological effects of the major adrenal cortex hormone aldosterone

Answer 18

aldosterone-most potent mineralocorticoid - regulate electrolyte concentrations esp. Na+ and K+, blood volume and pressure, stimulate reabsorption of Na+ in DST & CD of kidneys, water follows, decrease urine output, stimulates elimination of K+ because more Na+-K+ pumps

hypothalamus releases corticotropin releasing hormone → anterior pituitary releases adrenocorticotropic hormone → adrenal cortex releases hormones including aldosterone

ANP inhibits aldosterone

Question 19

List and explain the effects of the two hormones secreted by the adrenal medulla.

Answer 19

“misplaced sympathetic ganglion,” composed of chromaffin cells, synthesizes catecholamines including E and NE which both bind adrenergic receptors (E has stronger affinity)

increased CO, blood glucose, vasoconstriction, HR, all of which makes blood with vital nutrients go to 🧠 , ♥️ , 💪 , sympathetic fight or flight response

responses to stressors are brief, unlike cortical hormones, duration is lower

Question 20

Explain the physiological effects of long-term stress.

Answer 20

adrenal cortex releases mineralocorticoids like aldosterone - retention of sodium and H20 by kidneys → increased BV and BP → can lead to HTN

glucocorticoids - cortisol - proteins/fats broken down for energy/converted to glucose → increased blood glucose, suppressed immune system

Question 21

Describe the location, structure, and function of the pineal gland.

Answer 21

hanging from the roof of third ventricle in epithalamus superior to corpora quadrigemina

its cells called pinealocytes secrete melatonin

Question 22

Explain the functions of melatonin in the body.

Answer 22

pinealocytes secrete melatonin, may affect timing of sexual maturation/puberty, day/night cycles, body temp/sleep/appetite, production of antioxidant/detox molecules in cells

Question 23

Differentiate alpha cells and beta cells.

Answer 23

alpha make glucagon - hyperglycemic, raises [glucose]

beta make insulin - hypoglycemic, lowers [glucose]

antagonistic, part of neg feedback to maintain blood glucose level

Question 24

Explain the effects of glucagon and insulin in the human body.

Answer 24

90mg/100ml is appropriate level of [glucose]

stimulus of low [glucose] in blood makes pancreas release glucagon, stimulates liver to break glycogen down into glucose, dump it into blood

stimulus of high [glucose] makes pancreas release insulin, tells liver to take glucose from blood and store it for later, also stimulates tissues in body to take glucose from blood and use it for cellular metabolism

Question 25

Discuss diabetes insipidus including causes of each kind.

Answer 25

insipidus - low ACH (central) or resistance to ACH by kidneys (nephrogenic)

central diabetes insipidus causes

• idiopathic
• neurosurgery, head trauma, pituitary tumor

nephrogenic diabetes insipidus causes

• lithium toxicity
• renal disease
• hypokalemia
• pregnancy
• medications

Question 26

Differentiate type I and type II diabetes mellitus.

Answer 26

type I – autoimmune, body destroys beta cells in pancreatic islets, cannot make insulin, large amount of glucose but no insulin, supplement insulin to have it stimulate glucose uptake, cells completely absent, so diet and lifestyle will not manage it on their own

type II -

• functioning beta cells, down-regulation from prolonged elevated blood glucose → elevated levels of insulin in blood more of the time → fewer receptors for insulin over time

OR

• intracellular defects, transporters remain inactive even when present
• either way, cells are resistant to insulin
• can be managed with diet/exercise sometimes
• now more common in children, used to be adult onset

Question 27

Explain the pathology of diabetes mellitus, including causes and 3 cardinal signs & other symptoms.

Answer 27

mellitus - insulin/glucose dysregulation, glucose in urine, low levels of insulin → no longer have negative feedback loop w/insulin effect → tissue cells take up less glucose and use less → liver stops using glucose to make glycogen, instead breaks down glycogen → skeletal muscle breaks down proteins, liver uses AAs to build glucose for blood → spike in [glucose] in blood, hyperglycemia, filtrate has high levels of glucose → osmotic diuretic prevents water from being reabsorbed, glucose exceeds transport max, high urine output = polyuria → dehydration → thirstiness = polydipsia, breakdown of fat and protein leads to excessive hunger = polyphagia,

diabetic ketoacidosis from too much fat breakdown generating ketone bodies and lowering pH of blood too much, lose positively charged ions → electrolyte imbalances → arrhythmia, depression of CNS, cardiac arrest; body trying to rid itself of excess ketones - rapid breathing, fruity breath, nausea, vomiting

Question 28

hyperprolactinemia

Answer 28

galactorrhea (milk production) in men or women, infertility and/or menstrual regularity in women

more severe for men: impotence, visual problems, headache, add’l ant. pituitary issues

Question 29

effects of thyroid hormone

Answer 29

increase basal metabolic rate to burn calories, regulate growth/development of tissues, maintain BP

Question 30

glucocorticoids especially cortisol

Answer 30

major hormone is cortisol, influence metabolism to resist stressors, keep blood glucose relatively constant and maintain BP

cortisol increases blood glucose, fatty acids and AAs, stimulates gluconeogenesis to use fatty acids and AAs as fuel for other cells to “save” glucose in blood 🩸 for 🧠

vasoconstriction to raise BP to quickly distribute nutrients

Question 31

gonadocorticoids-describe and discuss importance

Answer 31

weak androgens converted to testosterone/estrogen

may contribute to onset of puberty, secondary sex characteristics, sex drive in women, source of estrogen in postmenopausal women

Question 32

What is the role of the protein kinases in a cell?

Answer 32

Protein kinases are enzymes that, when activated by a second messenger, phosphorylate (give a phosphate group to) other proteins. This may activate or inhibit various cellular processes.

Question 33

What’s special about thyroid hormone?

Answer 33

Although thyroid hormone is composed of amino acids, it is lipid soluble and capable of crossing the plasma membrane.

Question 34

What are steroids?

Answer 34

Steroid hormones are derived from the cholesterol molecule, a ring-shaped lipid. They include the sex hormones produced in the gonad and the hormones produced by the adrenal cortex.

Question 35

Which of the following does anterior pituitary not produce?

thyroid hormone

adrenocorticotropic hormone

prolactin

follicle-stimulating hormone

Answer 35

thyroid hormone

Question 36

site that receives the blood and hormones from the primary plexus and into which hormones such as GH, TSH, and ACTH are secreted

Answer 36

secondary capillary plexus

Question 37

Trace a releasing hormone from its synthesis through its pathway to stimulation of anterior pituitary hormones. Begin with the site of releasing hormone (RH) or inhibiting hormone (IH) synthesis.

Answer 37

Question 38

long-term stress from hypothalamus to effector organs

Answer 38

In the long-term stress response, stressful stimuli cause the hypothalamus to release corticotropin-releasing hormone, or CRH. CRH then travels through the hypothalamic portal system to the anterior lobe of the pituitary gland. The anterior pituitary releases adrenocorticotropic hormone, or ACTH, which travels via the blood to the adrenal gland. The adrenal cortex is the specific target for ACTH, which produces more glucocorticoids, chiefly cortisol, and mineralocorticoids, namely aldosterone. As you have seen, glucocorticoids have pronounced metabolic effects on the liver, while the mineralocorticoids target the kidney to retain more water and sodium, resulting in increased blood pressure and blood volume.

Question 39

which hormone targets the adrenal gland to release glucocorticoids and mineralocorticoids

Answer 39

Adrenocorticotropic hormone

Question 40

Which hormone stimulates the anterior pituitary to release ACTH

Answer 40

Corticotropin-releasing hormone

Question 41

Differentiate short and long-term stress

Answer 41

Question 42

Insulin plays a vital role in carbohydrate metabolism. What is its role?

Answer 42

Insulin is needed for cells to pick up glucose from the blood; without insulin, more glucose will remain in the blood.

Question 43

FSH and LH belong in which hormone category?

Answer 43

FSH and LH belong in the gonadotropins category of hormones.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (lu’te-in-īz”ing) are referred to collectively as gonadotropins. They regulate the function of the gonads (ovaries and testes). In both sexes, FSH stimulates production of gametes (sperm or eggs) and LH promotes production of gonadal hormones. In females, LH works with FSH to cause an eggcontaining ovarian follicle to mature. LH then triggers ovulation and promotes synthesis and release of ovarian hormones. In males, LH stimulates the interstitial cells of the testes to produce the male hormone testosterone.

Question 44

What stimulates production of FSH?

Answer 44

gonadotropin-releasing hormone (GnRH)

Question 45

Where does thyroxine come from?

Answer 45

The site of production for thyroxine is the thyroid gland. The butterfly-shaped thyroid gland is located in the anterior neck, on the trachea just inferior to the larynx. Internally, the gland is composed of hollow, spherical follicles. The follicular cells produce thyroglobulin. Thyroid hormone is derived from iodinated thyroglobulin.

Question 46

anterior pituitary gland’s communication, 6 hormones, and what’s different about growth hormone

Answer 46

communicates with hypothalamus via hypophyseal portal system, hypothalamus talks to anterior pituitary with hormones to tell it to release/not release its tropic hormones,

growth, thyroid-stimulating, adrenocorticotropic, follicle-stimulating, luteinizing, prolactin

(growth hormone’s main actions are not in the body’s glands, but instead other tissues)

Question 47

anti-insulin (metabolic) effect of growth hormone

Answer 47

growth hormone usually stops some tissues from taking up glucose to conserve it for tissues that need it to grow, increases fat breakdown and release

Question 48

Which hormone has positive feedback loop rather than negative? How does that work?

Answer 48

prolactin (milk production hormone) is typically inhibited by PIH, inhibition is relieved by rising levels of estrogen just before lactation, prolactin release → higher activity of mammary glands → act of nursing stimulates prolactin → stimulates more milk production

Question 49

explain connection between iodide/iodine and goiter

Answer 49

if you don’t have iodine, can’t bring tyrosines back into follicular cells on their way to the bloodstream, so the thyroid gets massive as the colloid gets overwhelmed