Endocrine Physiology Flashcards
Where are the receptors of water-soluble hormones found?
Cell Membrane Lipid-soluble: Nuclear/cytoplasmic
What is the final effect of lipid hormones on intracellular enzymes?
Synthesizes NEW enzymes
Water-soluble: Activate existing
What is the most important subunit of the g-proteins?
α subunit
binds with GDP (inactivates G protein) or GTP (activates G protein)
What is the general sequence of utilizing the 2nd messengers?
1st messenger (hormone/NT) → G-protein coupled receptors (cell membrane receptors!) for hormones/NTs → G Proteins → 2nd Messengers →→→ kinases → activated enzyme → intracellular response
What is the most common 2nd messenger system?
cAMP
Alpha subunit of G proteins activates
Adenylate cyclase converts ATP to cAMP → activates Protein Kinase A (PKA)
What is the 2nd messenger system used by all hypothalamic hormones except CRH?
IP3/DAG
What are the four common substances that use Guanylyl Cyclase for catalytic receptor mechanisms?
ANP, BNP, EDRF, NO
What does insulin use as a 2nd messenger system?
Receptor Tyrosine Kinase
What substance uses the Serine / Threonine kinase system?
TGF-B
What 2nd messenger system has no intrinsic catalytic activity?
Tyrosine-associated kinase
What are the hormones secreted by the acidophilic cells of the pituitary?
GH, Prolactin
Which group of hormones have the same alpha unit but unique beta unit?
TSH, LH, FSH
Which group of hormones are derived from cholesterol?
Steroid Hormones
Glucocorticoids
Mineralocorticoids
Sex Hormones
What are the hormones derived from POMC?
MSH, ACTH, betalipotropin, beta-endorphin
What hormones are homologous to prolactin?
GH, HPL
What hormones resemble glucagon in maintaining blood sugar levels?
Epinephrine, Cortisol, Growth Hormone
What is the effect of starvation, deep sleep, and hyperglycemia on GH secretion, respectively?
Increase – Increase – Decrease
The indirect effect of the GH is carried out by what substance / hormone?
IGF-1
Indirect effects: ↑ Bone Length and
Thickness (pubertal growth spurt), ↑ protein synthesis in muscles and other organs and ↑ lean body mass, ↑ organ size
What hormone is responsible for lactogenesis?
Prolactin
What is the effect of prolactin on ovulation?
Inhibits ovulation (and spermatogenesis)
Inhibits GnRH
What is the effect of TRH and dopamine on prolactin secretion, respectively?
Increases - Decreases
What pituitary hormone responds to ECF changes detected by osmoreceptors in the organum vasculosum?
Anti-Diuretic Hormone (ADH) or Arginine Vasopressin (AVP)
What is the most potent stimulus for ADH secretion?
Increase plasma osmolarity
What is the effect of ADH on V1 and V2 receptors?
V1: Vasoconstriction of arterioles
V2: insertion of AQP-2 in the late distal tubule and CD
What hormone is secreted from the Hypothalamic Paraventricular Nuclei?
Oxytocin
Other than suckling of breast, what are other stimuli for oxytocin secretion?
Cervical dilation, orgasm; sight, sound, and smell of infant
What is the transporter used to transport of I- to follicular lumen during thyroid hormone synthesis?
Pendrin
What steps in the thyroid hormone synthesis use PEROXIDASE?
Oxidation
Organification
Coupling
What type of transporter is used for iodide uptake in the basal membrane?
Secondary active transport (Na+I symporter)
What enzymes are used to convert T4 to T3?
Deiodinase Type 1 and Type 2
Outer ring deiodination
How many percent T3 are synthesized?
7%
This refers to the ingestion of a large amount of iodine that reduces T3 and T4:
Wolff-Chaikoff Effect
This refers to hyperthyroidism following small increased ingestion of iodine:
Jod-Basedow Phenomenon
What are the adrenal hormones
coming from the outer to the inner layer of the organ?
Z. Glomerulosa: Aldosterone
Z. Fasciculata: Cortisol
Z. Reticularis: Androstenedione
Medulla: 80%EPI, 20%Norepi
Which step in steroid hormone biosynthesis is stimulated by
adrenocorticotropic hormone
(ACTH)?
Cholesterol → pregnenolone
Which step in steroid hormone biosynthesis is stimulated by Angiotensin II?
Corticosterone → Aldosterone
What enzyme, if inhibited, will block the production of glucocorticoids and androgens, SPARING the mineralocorticoids?
17a-hydroxylase
What enzyme, if inhibited, will block the production of androgens, SPARING both the glucocorticoids and the mineralocorticoids?
17,20-lyase
What is the effect of aldosterone on Na+, K+, and H+?
↑ Na+ Reabsorption
↑ K+ Secretion
↑H+ Secretion
What transporter is increased by aldosterone?
ENaC: Epithelial Na Channels
Mole for mole, Na+ excretion is greatly affected by what hormone?
Aldosterone
Mole for mole, plasma osmolarity is greatly affected by what hormone?
ADH
What is the usual pattern of cortisol secretion?
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
How does cortisol maintain vascular responsiveness to catecholamines?
Upregulates alpha- 1 receptors on arterioles, increasing Epinephrine’s
vasoconstrictor effects →→ Increases BP
What adrenal disorder: Hyperglycemia, muscle wasting, central obesity, round face, supraclavicular fat, buffalo hump,
osteoporosis
Cushing Syndrome/Disease
What adrenal disorder: Hypertension, hypokalemia, metabolic alkalosis, decreased renin
Conn Syndrome
What adrenal disorder: Lack of pubic and axillary hair in women, with glucocorticoid
deficiency and mineralocorticoid excess
17-Alpha Hydroxylase deficiency
How does cortisol participate in the inflammation process?
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
What metabolic pathways are increased by Glucagon?
Increase glycogenolysis
Increase gluconeogenesis
What is the 2nd messenger of glucagon?
cAMP
What is the main stimulus of insulin secretion?
High blood glucose
In which muscles or organs does insulin increase glucose uptake?
Liver, skeletal muscle, adipose
What is the composition of bone?
30% Organic matrix
70% bone salts
Which part of the organic matrix provides the bone tensile strength?
Collagen fibers
What is the function of bone salts?
For compressional strength
Where is the majority of calcium found in the body?
99% as hydroxyapatite in Bone
What is the active form of vitamin D?
1,25 dihydroxycholecalciferol (calcitriol)
Increases intestinal Ca2+ absorption via alteration in activity of genes
What is the stimulus for PTH secretion?
Low plasma Ca++
What is the net effect of PTH and vitamin D on serum Ca+ and phosphate?
PTH: high calcium, low phosphate
Vitamin D: high calcium, high phosphate
How is phenotypic sex determined?
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
Where is sperm stored in the
physiologic male repro anatomy?
Epididymis
Which male repro-anatomy neutralizes the acidity of other fluids during ejaculation, enhancing the fertility of the sperm?
Prostate Gland
For semen alkalinity (using spermine); contains 5-alpha reductase that converts testosterone to DHT
This refers to the activation of sperm in the female genital tract:
Capacitation
What is the cut-off value of oligospermia?
< 15 million sperms/mL
What is the mechanism for the prevention of polyspermy?
Cortical reaction that modifies zona pellucida
What is the FSH and LH level during childhood and senescence?
FSH > LH
Childhood: both at their lowest
Senescence: both at their highest
How many percent are free testosterone in the blood?
2%
60% bound to Sex-Hormone Biding Globulin
38% bound to albumin
What hormone is responsible for the differentiation of penis, scrotum, and prostate?
Dihydrotestosterone
What hormone is responsible for the deepening of voice?
Testosterone
What are the target cells of FSH and LH, respectively?
FSH on Sertoli Cells
LH on Leydig Cells
Which cell in the male reproductive system produces testosterone?
Leydig – testosterone
Sertoli – Androgen Binding Protein and Inhibin
What does FSH stimulate or do in the male reproductive system?
FSH stimulates Sertoli Cells to release Androgen Binding Protein and Inhibin (Negative Feedback)
What is the output or product of the 1st meiotic division in spermatogenesis?
primary spermatocytes become secondary spermatocytes (haploid)
What process results from spermatids changing their shape to become spermatozoons?
Spermiogenesis
What step in Spermatogenesis is where all 46 chromosomes replicate?
Meiosis I
Where are the three forms of estrogen secreted?
Estrone: secreted by the adrenal cortex and thecal cell
Estradiol: secreted by ovaries
Estriol: secreted by placenta
What enzyme is needed for the development of female (NOT MALE) secondary sex characteristics?
Aromatase
What process is catalyzed by aromatase?
conversion of Androstenedione →
Estrone & Testosterone → Estradiol
What is the effect of progesterone on the endometrium?
Increases endometrial glandular secretion; Maintenance of secretory
activity of uterus during luteal phase
What hormone predominates during the Follicular Phase?
Estrogen
Luteal: Progesterone
What hormone predominates during the Proliferative Phase?
Estrogen
Secretory: Progesterone
What happens to the LH and FSH receptors during the follicular phase?
Upregulated
Primordial follicle develops to Graafian stage, with atresia of neighboring follicles
When does ovulation occur?
Occurs 14 days before menses regardless of cycle length
What causes menses?
Sloughing of endometrium due to abrupt cessation of estradiol and progesterone
When does implantation occur?
6-7 days after fertilization
When does B-HCG peak?
7-9 weeks
Start: 6-8 days ovulation
Decline: 20 weeks
What is the GnRH level during pregnancy?
Decreased
What are the organs that release estrogen during the second and third trimester?
fetal adrenal gland
fetal liver
placenta
The egg cell is arrested at what phase?
arrested at prophase I from
birth to puberty
Will proceed from prophase I to metaphase II during ovulation
Completion of meiosis during fertilization
What hormone relaxes pubic symphysis, softens, and dilates the cervix?
Relaxin
produced by corpus luteum, uterus, placenta and mammary gland, prostate gland
What hormone maintains sperm motility and aids in sperm penetration?
Relaxin
produced by corpus luteum, uterus, placenta and mammary gland, prostate gland
What is the trigger for the onset of labor?
Fetal ACTH
What is the final event required for the conversion of the newborn circulation to the adult pattern?
functional closure of the ductus arteriosus
What happens to the systemic vascular resistance upon a baby’s first breath?
Increased
↑ PaO2 → ↓ pulmonary vascular resistance
increased systemic vascular resistance
How long does prolactin inhibit ovulation?
6 months
due to inhibition of GnRH (preventing LH surge from ultimately happening)
Factors DECREASING GH secretion
HHAOSES
Hyperglycemia
High fatty acid levels
Aging
Obesity
Somatostatin
Exogenous GH
Somatomedin
