Endocrine Physiology

Question 1

Where are the receptors of water-soluble hormones found?

Answer 1

Cell Membrane Lipid-soluble: Nuclear/cytoplasmic

Question 2

What is the final effect of lipid hormones on intracellular enzymes?

Answer 2

Synthesizes NEW enzymes
Water-soluble: Activate existing

Question 3

What is the most important subunit of the g-proteins?

Answer 3

α subunit
binds with GDP (inactivates G protein) or GTP (activates G protein)

Question 4

What is the general sequence of utilizing the 2nd messengers?

Answer 4

1st messenger (hormone/NT) → G-protein coupled receptors (cell membrane receptors!) for hormones/NTs → G Proteins → 2nd Messengers →→→ kinases → activated enzyme → intracellular response

Question 5

What is the most common 2nd messenger system?

Answer 5

cAMP
Alpha subunit of G proteins activates
Adenylate cyclase converts ATP to cAMP → activates Protein Kinase A (PKA)

Question 6

What is the 2nd messenger system used by all hypothalamic hormones except CRH?

Answer 6

IP3/DAG

Question 7

What are the four common substances that use Guanylyl Cyclase for catalytic receptor mechanisms?

Answer 7

ANP, BNP, EDRF, NO

Question 8

What does insulin use as a 2nd messenger system?

Answer 8

Receptor Tyrosine Kinase

Question 9

What substance uses the Serine / Threonine kinase system?

Answer 9

TGF-B

Question 10

What 2nd messenger system has no intrinsic catalytic activity?

Answer 10

Tyrosine-associated kinase

Question 11

What are the hormones secreted by the acidophilic cells of the pituitary?

Answer 11

GH, Prolactin

Question 12

Which group of hormones have the same alpha unit but unique beta unit?

Answer 12

TSH, LH, FSH

Question 13

Which group of hormones are derived from cholesterol?

Answer 13

Steroid Hormones
Glucocorticoids
Mineralocorticoids
Sex Hormones

Question 14

What are the hormones derived from POMC?

Answer 14

MSH, ACTH, betalipotropin, beta-endorphin

Question 15

What hormones are homologous to prolactin?

Answer 15

GH, HPL

Question 16

What hormones resemble glucagon in maintaining blood sugar levels?

Answer 16

Epinephrine, Cortisol, Growth Hormone

Question 17

What is the effect of starvation, deep sleep, and hyperglycemia on GH secretion, respectively?

Answer 17

Increase – Increase – Decrease

Question 18

The indirect effect of the GH is carried out by what substance / hormone?

Answer 18

IGF-1
Indirect effects: ↑ Bone Length and
Thickness (pubertal growth spurt), ↑ protein synthesis in muscles and other organs and ↑ lean body mass, ↑ organ size

Question 19

What hormone is responsible for lactogenesis?

Answer 19

Prolactin

Question 20

What is the effect of prolactin on ovulation?

Answer 20

Inhibits ovulation (and spermatogenesis)
Inhibits GnRH

Question 21

What is the effect of TRH and dopamine on prolactin secretion, respectively?

Answer 21

Increases - Decreases

Question 22

What pituitary hormone responds to ECF changes detected by osmoreceptors in the organum vasculosum?

Answer 22

Anti-Diuretic Hormone (ADH) or Arginine Vasopressin (AVP)

Question 23

What is the most potent stimulus for ADH secretion?

Answer 23

Increase plasma osmolarity

Question 24

What is the effect of ADH on V1 and V2 receptors?

Answer 24

V1: Vasoconstriction of arterioles
V2: insertion of AQP-2 in the late distal tubule and CD

Question 25

What hormone is secreted from the Hypothalamic Paraventricular Nuclei?

Answer 25

Oxytocin

Question 26

Other than suckling of breast, what are other stimuli for oxytocin secretion?

Answer 26

Cervical dilation, orgasm; sight, sound, and smell of infant

Question 27

What is the transporter used to transport of I- to follicular lumen during thyroid hormone synthesis?

Answer 27

Pendrin

Question 28

What steps in the thyroid hormone synthesis use PEROXIDASE?

Answer 28

Oxidation Organification Coupling

Question 29

What type of transporter is used for iodide uptake in the basal membrane?

Answer 29

Secondary active transport (Na+I symporter)

Question 30

What enzymes are used to convert T4 to T3?

Answer 30

Deiodinase Type 1 and Type 2 Outer ring deiodination

Question 31

How many percent T3 are synthesized?

Answer 31

7%

Question 32

This refers to the ingestion of a large amount of iodine that reduces T3 and T4:

Answer 32

Wolff-Chaikoff Effect

Question 33

This refers to hyperthyroidism following small increased ingestion of iodine:

Answer 33

Jod-Basedow Phenomenon

Question 34

What are the adrenal hormones coming from the outer to the inner layer of the organ?

Answer 34

Z. Glomerulosa: Aldosterone Z. Fasciculata: Cortisol Z. Reticularis: Androstenedione Medulla: 80%EPI, 20%Norepi

Question 35

Which step in steroid hormone biosynthesis is stimulated by adrenocorticotropic hormone (ACTH)?

Answer 35

Cholesterol → pregnenolone

Question 36

Which step in steroid hormone biosynthesis is stimulated by Angiotensin II?

Answer 36

Corticosterone → Aldosterone

Question 37

What enzyme, if inhibited, will block the production of glucocorticoids and androgens, SPARING the mineralocorticoids?

Answer 37

17a-hydroxylase

Question 38

What enzyme, if inhibited, will block the production of androgens, SPARING both the glucocorticoids and the mineralocorticoids?

Answer 38

17,20-lyase

Question 39

What is the effect of aldosterone on Na+, K+, and H+?

Answer 39

↑ Na+ Reabsorption ↑ K+ Secretion ↑H+ Secretion

Question 40

What transporter is increased by aldosterone?

Answer 40

ENaC: Epithelial Na Channels

Question 41

Mole for mole, Na+ excretion is greatly affected by what hormone?

Answer 41

Aldosterone

Question 42

Mole for mole, plasma osmolarity is greatly affected by what hormone?

Answer 42

ADH

Question 43

What is the usual pattern of cortisol secretion?

Answer 43

Oscillates with circadian rhythm Highest levels: before waking up (8am) Lowest levels: in the evening (midnight) Rise sharply during sleep, peak soon after awakening, sink to a low level 12 hours later

Question 44

How does cortisol maintain vascular responsiveness to catecholamines?

Answer 44

Upregulates alpha- 1 receptors on arterioles, increasing Epinephrine’s vasoconstrictor effects →→ Increases BP

Question 45

What adrenal disorder: Hyperglycemia, muscle wasting, central obesity, round face, supraclavicular fat, buffalo hump, osteoporosis

Answer 45

Cushing Syndrome/Disease

Question 46

What adrenal disorder: Hypertension, hypokalemia, metabolic alkalosis, decreased renin

Answer 46

Conn Syndrome

Question 47

What adrenal disorder: Lack of pubic and axillary hair in women, with glucocorticoid deficiency and mineralocorticoid excess

Answer 47

17-Alpha Hydroxylase deficiency

Question 48

How does cortisol participate in the inflammation process?

Answer 48

Exerts ANTI-inflammatory inhibits Phospholipase A2 needed for PG and LT synthesis Decreases migration and phagocytosis of WBCs Suppression of T-lymphocytes ↓ IL-1, IL-2 ↑ resolution of inflammation Blocks inflammatory response to allergies ↓ eosinophils and lymphocytes Inhibits histamine and serotonin release

Question 49

What metabolic pathways are increased by Glucagon?

Answer 49

Increase glycogenolysis Increase gluconeogenesis

Question 50

What is the 2nd messenger of glucagon?

Answer 50

cAMP

Question 51

What is the main stimulus of insulin secretion?

Answer 51

High blood glucose

Question 52

In which muscles or organs does insulin increase glucose uptake?

Answer 52

Liver, skeletal muscle, adipose

Question 53

What is the composition of bone?

Answer 53

30% Organic matrix 70% bone salts

Question 54

Which part of the organic matrix provides the bone tensile strength?

Answer 54

Collagen fibers

Question 55

What is the function of bone salts?

Answer 55

For compressional strength

Question 56

Where is the majority of calcium found in the body?

Answer 56

99% as hydroxyapatite in Bone

Question 57

What is the active form of vitamin D?

Answer 57

1,25 dihydroxycholecalciferol (calcitriol) Increases intestinal Ca2+ absorption via alteration in activity of genes

Question 58

What is the stimulus for PTH secretion?

Answer 58

Low plasma Ca++

Question 59

What is the net effect of PTH and vitamin D on serum Ca+ and phosphate?

Answer 59

PTH: high calcium, low phosphate Vitamin D: high calcium, high phosphate

Question 60

How is phenotypic sex determined?

Answer 60

by characteristics of the internal genital tract and external genitalia Genetic Sex: determined by sex chromosomes Gonadal Sex: determined by the presence of testes in males and ovaries in females

Question 61

Where is sperm stored in the physiologic male repro anatomy?

Answer 61

Epididymis

Question 62

Which male repro-anatomy neutralizes the acidity of other fluids during ejaculation, enhancing the fertility of the sperm?

Answer 62

Prostate Gland For semen alkalinity (using spermine); contains 5-alpha reductase that converts testosterone to DHT

Question 63

This refers to the activation of sperm in the female genital tract:

Answer 63

Capacitation

Question 64

What is the cut-off value of oligospermia?

Answer 64

< 15 million sperms/mL

Question 65

What is the mechanism for the prevention of polyspermy?

Answer 65

Cortical reaction that modifies zona pellucida

Question 66

What is the FSH and LH level during childhood and senescence?

Answer 66

FSH > LH Childhood: both at their lowest Senescence: both at their highest

Question 67

How many percent are free testosterone in the blood?

Answer 67

2% 60% bound to Sex-Hormone Biding Globulin 38% bound to albumin

Question 68

What hormone is responsible for the differentiation of penis, scrotum, and prostate?

Answer 68

Dihydrotestosterone

Question 69

What hormone is responsible for the deepening of voice?

Answer 69

Testosterone

Question 70

What are the target cells of FSH and LH, respectively?

Answer 70

FSH on Sertoli Cells LH on Leydig Cells

Question 71

Which cell in the male reproductive system produces testosterone?

Answer 71

Leydig – testosterone Sertoli – Androgen Binding Protein and Inhibin

Question 72

What does FSH stimulate or do in the male reproductive system?

Answer 72

FSH stimulates Sertoli Cells to release Androgen Binding Protein and Inhibin (Negative Feedback)

Question 73

What is the output or product of the 1st meiotic division in spermatogenesis?

Answer 73

primary spermatocytes become secondary spermatocytes (haploid)

Question 74

What process results from spermatids changing their shape to become spermatozoons?

Answer 74

Spermiogenesis

Question 75

What step in Spermatogenesis is where all 46 chromosomes replicate?

Answer 75

Meiosis I

Question 76

Where are the three forms of estrogen secreted?

Answer 76

Estrone: secreted by the adrenal cortex and thecal cell Estradiol: secreted by ovaries Estriol: secreted by placenta

Question 77

What enzyme is needed for the development of female (NOT MALE) secondary sex characteristics?

Answer 77

Aromatase

Question 78

What process is catalyzed by aromatase?

Answer 78

conversion of Androstenedione → Estrone & Testosterone → Estradiol

Question 79

What is the effect of progesterone on the endometrium?

Answer 79

Increases endometrial glandular secretion; Maintenance of secretory activity of uterus during luteal phase

Question 80

What hormone predominates during the Follicular Phase?

Answer 80

Estrogen Luteal: Progesterone

Question 81

What hormone predominates during the Proliferative Phase?

Answer 81

Estrogen Secretory: Progesterone

Question 82

What happens to the LH and FSH receptors during the follicular phase?

Answer 82

Upregulated Primordial follicle develops to Graafian stage, with atresia of neighboring follicles

Question 83

When does ovulation occur?

Answer 83

Occurs 14 days before menses regardless of cycle length

Question 84

What causes menses?

Answer 84

Sloughing of endometrium due to abrupt cessation of estradiol and progesterone

Question 85

When does implantation occur?

Answer 85

6-7 days after fertilization

Question 86

When does B-HCG peak?

Answer 86

7-9 weeks Start: 6-8 days ovulation Decline: 20 weeks

Question 87

What is the GnRH level during pregnancy?

Answer 87

Decreased

Question 88

What are the organs that release estrogen during the second and third trimester?

Answer 88

fetal adrenal gland fetal liver placenta

Question 89

The egg cell is arrested at what phase?

Answer 89

arrested at prophase I from birth to puberty Will proceed from prophase I to metaphase II during ovulation Completion of meiosis during fertilization

Question 90

What hormone relaxes pubic symphysis, softens, and dilates the cervix?

Answer 90

Relaxin produced by corpus luteum, uterus, placenta and mammary gland, prostate gland

Question 91

What hormone maintains sperm motility and aids in sperm penetration?

Answer 91

Relaxin produced by corpus luteum, uterus, placenta and mammary gland, prostate gland

Question 92

What is the trigger for the onset of labor?

Answer 92

Fetal ACTH

Question 93

What is the final event required for the conversion of the newborn circulation to the adult pattern?

Answer 93

functional closure of the ductus arteriosus

Question 94

What happens to the systemic vascular resistance upon a baby’s first breath?

Answer 94

Increased ↑ PaO2 → ↓ pulmonary vascular resistance increased systemic vascular resistance

Question 95

How long does prolactin inhibit ovulation?

Answer 95

6 months due to inhibition of GnRH (preventing LH surge from ultimately happening)

Question 96

Factors DECREASING GH secretion

Answer 96

HHAOSES Hyperglycemia High fatty acid levels Aging Obesity Somatostatin Exogenous GH Somatomedin