Module 1: Basic Principles of Endocrinology Flashcards
1
Q
What is endocrinology?
A
- science of hormones and glands that secrete them
- science of endocrine systems (hormones), their diseases, and therapies
2
Q
chemical released by a cell, gland, or organ in ONE PART of the body that affects cells in OTHER PARTS of the body (travels to distant sites)
A
Hormone
3
Q
Hormones = internal secretion by __________ glands
A
ductless
4
Q
What does intercellular communication require (3)?
A
- Signaling cell (origin of the signal)
- Messenger (chemical signal = hormone)
- Target cell (specific receptors)
5
Q
Factor within cell
A
intracrine
6
Q
the same cell, factor stays local
A
Autocrine
7
Q
different cells in proximity, factor stays local
A
Paracrine
8
Q
different cell - distant, factor carried in blood
A
Endocrine
9
Q
Cortisol, aldosterone, catecholamines
metabolism, minerals/pressure, stress, immunity
A
adrenal gland
10
Q
sex steroids, reproduction
A
gonads
11
Q
What do endocrine glands often regulate?
A
other endocrine organs
12
Q
Most endocrine glands produce ________ hormones
A
few
13
Q
Pituitary gland produces ______ hormones
A
many
14
Q
What do hormones from various endocrine organs influence?
A
the hypothalamus and pituitary
15
Q
The hormone concentrations are:
A
very low
16
Q
(T/F) Not all cells respond to a hormone
A
True
17
Q
(T/F) Hormones contact all cells
A
True
18
Q
What defines target tissue?
A
Receptor expression
19
Q
- Sensitive and Specific
- Generates an intracellular signal
A
Receptor-hormone binding
20
Q
Epinephrine, thyroid hormones (T3, T4)
A
Amines
21
Q
Parathyroid hormone, insulin, ACTH
A
Peptides
22
Q
Glucocorticoids, estrogens, vitamin D (from cholesterol)
A
Steroids
23
Q
Lipophilic =
A
hydrophobic
24
Q
Hydrophilic =
A
lipophobic
25
- Relatively SMALL molecular weight
- Cross membranes (lipid soluble)
- NOT STORED inside signaling cells (e.g. steroids, THs)
- Synthesis by MULTI-STEP enzymatic processes
- Bind INTRACELLULAR receptors
- Released SLOWER - work SLOWER - cleared SLOWER than hydrophilic
Lipophilic hormones
26
- Proteins, peptides, amines (first messenger)
- LARGE molecular weight (except amines)
- mRNA-directed synthesis (if proteins)
- DO NOT CROSS cell membrane
- STORED in intracellular vesicles
- Released FASTER - work FASTER - cleared FASTER than lipophilic
- Bind to receptors ON PLASMA MEMBRANE
- Use SECOND MESSENGER -> SIGNAL AMPLIFICATION
Hydrophilic hormones
27
Receptors:
- Found in the CYTOPLASM or NUCLEUS
- HORMONES + RECEPTOR COMPLEX -> nucleus to FUNCTION AS TRANSCRIPTION FACTOR -> mRNA synthesis -> protein synthesis
examples: steroids (cortisol, progesterone, estrogen), vitamin D, THs
Receptors of lipophilic hormones
28
Receptors:
- PROTEINS in CELL MEMBRANE of target cells
- Bind with SPECIFICITY and HIGH AFFINITY
- Activate SECOND MESSENGERS to generate an intracellular signal
- Stimulate a functional change in the target cell
Receptors for hydrophilic hormones
29
Receptors:
Receptor Tyrosine Kinases (RTK's): (in cell membrane)
- Receptors for peptide hormones, growth factors, cytokines
Receptors for hydrophilic hormones
30
Receptors:
7 Trans-membrane (7TM) family (GPCR): in cell membrane
- Receptors for peptide and amine hormones
Receptors for hydrophilic hormones
31
Minimal hormone level that elicits a cellular response
- receptors are highly sensitive to low hormone levels
Sensitivity
32
Receptors ability to bind a specific hormone (ability to differentiate different hormones)
- Receptors are highly specific to hormones within a family (some cross-reactivity)
Specificity
33
How can hormones generate a biological response at very low levels?
Signal Amplification
- H + R <--> HR -> 2nd messenger (x500) -> effector (x500)
34
What are most feedback loops?
most feedback loops are negative
35
- essential autoregulatory systems
- regulate most endocrine systems
- they could be used DIAGNOSTICALLY
- they could be used THERAPEUTICALLY
- abnormal leads to disorders
Feedback Systems
36
when the product of a reaction leads to an increase in that reaction
positive feedback loop
37
- a reaction that causes a decrease in function
- it occurs in response to some kind of stimulus
- often, it causes the output of a system to be lessened; so, the feedback tends to stabilize the system.
negative feedback loop
38
Hormone Transport:
__________- hormones are transported DISSOLVED in the extracellular fluid (blood) -> target
Hydrophilic
39
Hormone Transport:
___________ hormones are transported BOUND to protein
Lipophilic
40
What percentage of lipophilic hormones are protein-bound?
>90% are protein-bound
(there are specific binding proteins)
41
Why are>90% of steroid and thyroid hormones bound to plasma proteins in equilibrium?
- they are lipophilic
- act as a reservoir
- reduce their waste in urine
- protect against toxicity
- the same principle applies to some drugs
- binding proteins are specific to hormones
42
What prevents hormone renal waste?
Protein binding
43
Hormone Clearance:
Clearance is determined by...
- Rate of synthesis and secretion
- Rate of removal from circulation
44
Hormone Clearance:
Metabolized and excreted by...
- mainly by the liver (-> bile) and kidneys (->urine)
- by other organs (e.g. lungs) and target tissues
- Enzymes in circulation also degrade peptide hormones
- Peptides/amines cleared faster than protein-bound hormones
45
Hormones have daily variation influence by:
- physiological statue
- diet
- time of the day (circadian)
- time of the year (circannual)
- treatments
- stress
- diseases
- lack of variations can be pathologic
46
How are hormones measured?
Immunoassays
- Enzyme-linked immunoassays (ELISA)
- Radioimmunoassay (RIA)
- Chemiluminescent immunoassay (CLIA)
47
Hormone deficiency and hormone excess are problems at what level?
Endocrine gland level
48
Hormone resistance is a problem at what level?
Receptor Signaling level
(e.g. downregulation)
49
Type of endocrine disorder:
- Insufficient secretion of hormone
- Hypo...
Hormone deficiency
50
Type of endocrine disorder:
- Excessive secretion of hormone
- Hyper...
Hormone excess
51
Type of endocrine disorder:
- Hormone is secreted
- Actions are suboptimal (like hypo)
- Often increased concentrations
Hormone resistance
52
How do we suspect that there is an endocrinopathy?
1. Clinical Abnormalities
2. Changes in Behavior
3. Changes in blood variables
53
How do we test endocrine systems?
- Hormone concentrations
- Dynamic Tests
54
Single measurements
• Glucose, calcium (analytes)
• Insulin, cortisol, parathyroid hormone (PTH)
Paired measurements (feedback components)
• Glucose + Insulin
• Calcium + PTH
• Cortisol + ACTH
Hormone Concentrations
55
Stimulation (for deficiencies / hypoactivity)
• Give glucose → measure insulin response (+) ↑↑
• Give ACTH → measure cortisol response (+) ↑↑
Suppression (for excess/hyperactivity)
• Give calcium → measure PTH response (-) ↓↓
• Give cortisol →measure ACTH response (-) ↓↓
Dynamic Tests
56
What dynamic test evaluates the functionality of the endocrine system?
Stimulation
(for deficiencies/hypoactivity)
57
Which dynamic test evaluates negative feedback?
Suppression
(for excess/hyperactivity)
58
When testing the endocrine systems, what do you need to take into consideration?
- take into account environmental factors, diseases, drugs, and other endocrine systems that alter hormones
- interpret results in context of the whole animal
- looking at isolated test results is rarely useful
- equivocal results may require other tests
59
Progesterone binds to an ___________ receptor
intracellular
(steroid)
60
Glucagon binds to an _______________ receptor
cell membrane
(peptide)
61
Protein-bound in circulation
Lipophilic hormone
62
Reduces hormone excretion
Protein binding
63
Likely a peptide hormone
Stored in granules
64
Soluble in plasma
Epinephrine
65
Tissue resistance
Requires higher levels to exert an effect
