Lecture 1: Intro to Endocrinology Flashcards
Which hormones arise from the Hypothalamus; what’s their main action?
- TRH: stimulates secretion of TSH and prolactin
- CRH: stimulates secretion of ACTH
- GnRH: stimulates secretion of LH and FSH
- Somatostatin: inhibits secretion of GH
- Dopamine: inhibits secretion of prolactine
Which hormones arise from the Anterior Pituitary gland; main function of each?
- TSH: stimulates synthesis/secretion of thyroid hormones
- FSH: sperm maturation (males)/follicular dev. and estrogen synthesis (females)
- LH: testosterone synthesis (males)/ovulation, formation of corpus luteum, estrogen, and progesterone synthesis in ovaries (females)
- ACTH: synthesis and secretion of cortisol, androgens, aldoesterone
- MSH: melanin synthesis
- Growth Hormone: protein synthesis and overall growth
- Prolactin: milk production and secretion in breast
Which hormones arise from the Posterior Pituitary; function of each?
- ADH: water reabsorption in principle cells of collecting ducts and constriction of arterioles
- Oxytocin: milk ejection from breasts and uterine contraction
Which hormones arise from the Thyroid gland?
- T3, T4: skeletal growth; O2 consumption; heat prod.; protein, fat, and CHO utilization; perinatal maturation of CNS
- Calcitonin: decreases serum [Ca2+]
How are protein and peptide hormones usually synthesized and describe their route to becoming active?
- Synthesized as preprohormones (not biologically active)
- Signal peptide removed in the ER to produce prohormone
- Once they are packed into vesicles they are cleaved by proteolytic enzymes generating the active form
What can act as a stimulus for exocytosis of peptide/protein hormones from secretory vesicles?
- Increased intracellular Ca2+ caused by membrane depolarization
- Activation of GPCR’s, followed by increased cAMP and activation of PKA
What are the steroid hormones?
- Cortisol
- Aldosterone
- Estradiol
- Progesterone
- Testosterone
- 1,25-dihydroxycholecalciferol
The steroid hormones are synthesized and secreted from what 3 structures?
- Adrenal cortex
- Gonads
- Corpus luteum
What are the 2 sources of cholesterol for the synthesis of steroid hormones?
- LDL particles taken up through receptor-mediated endocytosis
- De novo synthesis for acetyl CoA
What are the genomic vs. nongenomic actions of steroid hormones?
Genomic (common theory): modulate gene transcription by interaction w/ intracellular, nuclear receptors
Nongenomic: rapid steroid actions. Specific-receptor-mediated actions or direct steroid-membrane interactions
Where are amine hormones dervied from and what are the 2 classification groups; how does each group act on its receptor?
- Derived from tyrosine
1) Catecholamines - act through cell-membrane associated receptors
2) Thyroid hormones - cross cell membrane and act thru nuclear receptors
What hormone comes from the Parathyroid gland and what is its function?
PTH: increases serum [Ca2+]
What hormones are secreted by the Adrenal Cortex and what are their functions?
- Cortisol: stimulates gluconeogenesis; inhibits inflammatory response; suppresses immune response; enhances vascular responsiveness to catecholamines
- Aldosterone: increases renal Na+ reabsorption, K+ secretion, and H+ secretion
- DHEA: stimulates spermatogenesis; stimulates male secondary sex characteristics
Which hormones are secreted from the Ovaries and Corpus Luteum; what are their actions?
- Estradiol: stimulates growth/development of female repro. system. follicular phase of menstrual cycle, dev. of breasts, prolactin secretion; maintains pregnancy
- Progesterone: stimulates luteal phase of menstrual cycle; maintains pregnancy
What hormones are secreted from the placenta and what are their actions?
- HCG: stimulates estrogen and progesterone synthesis in corpus luteum of early pregnancy
- hPL: has growth hormone-like and prolactin-like actions during pregnancy
- Estriol: same actions of estradiol
- Progesterone
Which hormones are secreted by the kidney and their actions?
- Renin: catalyzes conversion of angiotensinogen to angiotensin I
- 1,25-dihydroxycholecalciferol: increases intestinal absorption of Ca2+; bone mineralization
How can the secretion of hormones be turned on and off?
1) Neural mechanism
2) Negative feedback: most common
3) Positive feedback: rare; leads to an explosive event (i.e., menstrual cycle, delivery of fetus)
What is long-loop feedback?
Hormone released from the 3rd tier (peripheral endocrine gland) feeds back all the way to the 1st tier (hypothalamus) and 2nd tier (pituitary)
What is short-loop feedback?
Hormone secreted from the 2nd tier feeds back to the 1st tier
What is ultra short-loop feedback?
Glands inhibits its own secretion
What are the 3 endocrine axes?
1) HPA = Hypothalamus - Pituitary - Adrenal gland
2) HPT = Hypothalamus - Pituitary - Thyroid gland
3) HPG = Hypothalamus - Pituitary - Gonads
What is response driven feedback; what is an example of this involving insulin?
- Secretion of a hormone is stimulated or inhibited by a change in the level of a specific extracellular signal
- Insulin regulates blood glucose levels. In turn, blood glucose concentrations turns on or off insulin secretion.
How is the first tier of the endocrine axes regulated and what are the major inputs?
- Highly regulated by neural inputs to the hypothalamus
1) Suprachiasmatic nucleus (SCN): impose a circadian rhythm on the secretion of hypothalamic releasing hormones and endocrine axes
2) Pineal gland: releases melatonin which feedback to the SCN information about day-night
Describe Up-regulation in regards to a low level of circulating hormones
- Increases receptor # or sensitivity of target tissue when hormone levels are low:
- Increase in the synthesis of new receptors
- Decrease in the degradation of existing receptors
- Activating receptors
