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Endocrine Physiology > Introduction > Flashcards

Introduction Flashcards

1
Q

Describe the general pathway for anterior pituitary secretions.

A

Hypothalamus –> ant. pituitary –> peripheral endocrine gland –> release of third hormone

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2
Q

Describe the general pathway for posterior pituitary secretions.

A

Hormones synthesized in neuronal cell bodies in hypothalamus –> released via synapses in posterior pituitary (oxytocin and ADH)

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3
Q

4 structural groups of hormones:

A
  • peptides/proteins
  • amino acid derivatives
  • steroids
  • fatty acid derivatives (eicosanoids)
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4
Q

Peptide/protein hormones are _____ soluble and are often _______ to achieve an active form.

A

water; proteolytically cleaved

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5
Q

Describe the general pathway for peptide/protein hormone formation.

A

Gene –> mRNA –> preprohormone –> glycosylation in ER –> prohormone (in Golgi) –> secretory vessels (often in active form; other times remains a prohormone, like angiotensin)

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6
Q

What are the 2 groups of hormones derived from tyrosine?

A

Thyroid hormones and catecholamines

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7
Q

Describe thyroid hormones.

A
  • “double” tyrosine with 3/4 iodines
  • produced by thyroid gland
  • lipid soluble
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8
Q

Describe catecholamines (epinephrine and norepinephrine)

A
  • neurohormones/transmitters
  • produced in adrenal medulla
  • water soluble (secreted like peptide hormones)
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9
Q

Besides tyrosine, what are two other amino acids used for hormone synthesis? What do they make?

A

Tryptophan
- serotonin, melatonin
Glutamic acid
- histamine

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10
Q

Steroid hormones are derived from _____ and are ______ soluble.

A

cholesterol in the mitochondria and ER; lipid

No packaging; synthesized and immediately released. Require a globulin carrier in the blood.

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11
Q

List the types of steroid hormones.

A
  • Glucocorticoids (cortisol)
  • Mineralocorticoids (aldosterone)
  • Androgens, estrogens, progestogens (testosterone, estradiol and estrone, progesterone)

Sugar, salt, sex

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12
Q

What is an example of a steroid secreted by one cell and converted to the active steroid by the target cell?

A

Androgen secreted by gonad and converted to estrogen in the brain.

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13
Q

What is the rate-limiting step of steroid hormone synthesis?

A

Transport of free cholesterol from cytoplasm into mitochondria; done by StAR (steroidogenic actue regulatory protein)

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14
Q

Cholesterol precursor comes from…

A
  • acetate (synthesis in cell)
  • cholesterol ester stores in intracellular lipid droplets
  • uptake of cholesterol-containing LDLs
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15
Q

What is a “vitamin” derived from cholesterol?

A

1,25-Dihydroxy Vitamin D3

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16
Q

What are eicosanoids? What are they derived from?

A

Prostaglandins, prostacyclins, leukotrienes, thromboxanes

Arachidonic acid; these hormones active for a very short time

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17
Q

What are the features of the stimulus response system?

A
  • Receipt of stimulus
  • Synthesis and secretion of hormone
  • Delivery of hormone to target cell
  • Evoking target cell response
  • Degradation of hormone
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18
Q

What 3 factors affect hormone concentration?

A
  • Rate of production
  • Rate of delivery
  • Rate of degradation and elimination
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19
Q

What is neural control?

A

Neural input to hypothalamus stimulates releasing factors to stimulates pituitary

20
Q

What is chronotropic control?

A

Endogenous neuronal rhythmicity

- diurnal, circadian (GH/cortisol), sleep-wake cycle, seasonal

21
Q

What is a circhoral rhythm?

A

Release every house

22
Q

What is an ultraradian rhythm?

A

Release > 1 hr but

23
Q

What is a circadian rhythem?

A

Release every 24 hrs

24
Q

GnRH is pulsatile. Given once hourly, ________. Given more slowly, _______. Given constantly, ________.

A

Normal gonadotropin secretion
Won’t maintain gonad function
Inhibits gonadotropin secretion, blocks gonadal steroid production (prostate cancer treatment)

25
Q

Long-acting GnRH analogs (leuproline) can treat…

A
  • precocious puberty
  • manipulate reproductive cycles
  • treatment of endometriosis, PCOS, uterine leiomyoma
26
Q

What is a negative feedback example?

A

LH from pituitary stimulates testosterone, which inhibits LH

27
Q

What is a positive feedback example? (rarer)

A

LH stimulation of estrogen, which stimulates LH surge at ovulation

28
Q

What is an example of substrate-hormone control?

A

As glucose increases, it stimulates the pancreas to secrete insulin.

29
Q

What are the water and lipid soluble hormones?

A

Water: catecholamines, peptide/protein hormones
Lipid: thyroid hormone, steroid hormones, Vitamin D3

30
Q

Describe water soluble hormone receptors.

A

Surface of target cell, second messenger system

31
Q

Describe lipid soluble hormone receptors.

A

Nucleus of cell (sometimes cytoplasm) - hormones can diffuse into the cell

32
Q

What are some second messenger systems?

A
  • Adenylate cyclase (cAMP)
  • Guanylate cyclase (cGMP)
  • Calcium and calmodulin; phospholipase C (DAG and IP3)
33
Q

Signal transduction mechanisms:

Activation of adenylate cyclase affects…

A

beta-adrenergic, LH, FSH, TSH, hCG, glucagon, vasopressin-V2, ACTH

34
Q

Signal transduction mechanisms:

Inhibition of adenylate cyclase affects…

A

alpha2-adrenergic, opioid, muscarinic cholinergic-M2

35
Q

Signal transduction mechanisms:

Increased phosphoinositide turnover affects…

A

alpha1-adrenergic, angiotensin II, muscarinic cholinergic-M3, vasopressin-V1

36
Q

Signal transduction mechanisms:

Tyrosine kinase activation affects…

A

insulin, growth factors, GH, prolactin

37
Q

Why are responses evoked by lipid soluble hormones usually slow?

A

Involves transcription/translation.

Receptor-hormone complex binds to response element (specific DNA sequence) to make desired mRNA

38
Q

What is homologous desensitization?

A

Hormonally-induced negative regulation of receptors - protects from toxic effects of hormone excess

39
Q

What is heterologous desensitization?

A

Occurs when exposure of the cell to one agonist reduces the responsiveness of the cell to another agonist that acts via a different receptor.
- most commonly in adenylate cyclase system

40
Q

Mechanisms of endocrine disease:

What is deficiency?

A

Due to destructive process occurring at gland where hormone is produced (infection, infarction, physical compression by tumor) - Type 1 diabetes (beta-cells)

OR

Genetic defects in production (gene deletion/mutation, failure to cleave precursor, enzymatic defect) - Congenital Adrenal Hyperplasia

41
Q

Deficiency can also arise from…

A

Genetic defects in production (gene deletion/mutation, failure to cleave precursor, enzymatic defect) - Congenital Adrenal Hyperplasia

42
Q

A third type of deficiency is caused by…

A

Inactivating mutations of receptors - Testicular Feminization Syndrome

43
Q

Mechanisms of endocrine disease:

What is excess?

A

Overproduction by gland or by a tissue that is not an endocrine organ; unregulated - Cushing’s Syndrome (cortisol)

44
Q

Another type of excess can be caused by… (an example is anabolic steroid usage)

A

Exogenous ingestion

45
Q

________ of cell surface receptors can cause aberrant stimulation of endocrine gland

A

Activating mutations

McCune-Albright Syndrome

46
Q

What causes Grave’s Disease?

A

Anti-receptor antibodies stimulate the receptor (instead of block it) - hyperthyroidism

47
Q

Alterations in the receptor number can also cause endocrine disorders; an aberrant ______ in hormone level can ______ available receptors

A

increase; decrease

Type II diabetes

Endocrine Physiology (7 decks)

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