Endocrine system and principles of hormone measurements

Question 1

hormones

Answer 1

chemical messengers from a gland or pocket of cells within an organ that regulate the activity of certain cells or organs

Question 2

neurotransmitters

Answer 2

synthesized in a pre-synaptic neuron and travel across a synapse to another neuron or to muscle

Question 3

neuroendocrine hormones

Answer 3

hormones produced by neuronal cells that are secreted into the bloodstream to act on distant cells (ex. neurons in hypothalamus release hormones into portal circulation to reach the anterior pituitary)

Question 4

most hormones are (small or polypeptides)

Answer 4

polypeptides

Question 5

Two main types of hormones

Answer 5

Lipid soluble

Water-soluble

Question 6

Steroid hormones

Answer 6

lipid soluble
Require carrier proteins to circulate in bloodstream
Diffuse directly into cells to bind CYTOSOLIC receptors

Question 7

Thyroid hormones

Answer 7

derived from tyrosine and iodine
lipid soluble
require carrier proteins to circulate in the bloodstream
diffuse directly into cells and bind NUCLEAR receptors

Question 8

Water soluble hormones

Answer 8

receptors on the cell surface
Amines are mainly derived from tyrosine
Peptides
Proteins (usually pro-hormones ex. proinsulin)
Glycoproteins

Question 9

C-peptide

Answer 9

an inactive derivative of proinsulin that can be used to asses the reserve capacity of the pancreas

Question 10

Albumin

Answer 10

a low affinity, high capacity hormone carrier

Question 11

free hormone

Answer 11

capable of producing a hormonal effect

Question 12

Simple control of the endocrine system

Answer 12

self limiting signal and effect

may have a threshold level to initiate response

Question 13

negative feedback

Answer 13

signal induces response, response inhibits production of signal
very common

Question 14

positive feedback

Answer 14

response amplifies original signal until system can no longer respond or signal is removed

Question 15

inhibitory control

Answer 15

release of hormone controlled by inhibitor, remove inhibitor to allow release
ex. prolactin release by anterior pituitary is inhibited by dopamine

Question 16

endocrine rhythms

Answer 16

pulsatility of hormones due to internal rhythms (ex. circadian)

Question 17

Over secretion

Answer 17

due to loss of feedback control through end organ failure, or:
ectopic production by alternate site

Question 18

Under-secretion

Answer 18

loss of stimulation

endocrine organ failure (ex. premature menopause as ovaries start to fail)

Question 19

Disordered Metabolic Pathway

Answer 19

may occur from reduced end product or increased intermediates that may or may not have endocrine activity (ex. congenital adrenal hyperplasia)

Question 20

Measurements of hormones: Bioassays

Answer 20

specific for biologically active hormones but are inaccurate, imprecise, inconvenient, time consuming, and expensive (ex. anti-TSH receptor)

Question 21

Chemical methods

Answer 21

depend on specific chemical markers on hormones (ex. -OH group on a steroid)
nonspecific, insensitive, and imprecise

Question 22

Chromatography

Answer 22

works well for small molecules (ex. neuroendocrine hormones, steroids)
prior to use of Tandem mass spectrometry

Question 23

Immunoassays

Answer 23

measure concentration, not activity
usually use monoclonal antibodies, sometimes polyclonal
automated (high throughput), accurate, precise
method of choice for large protein hormone molecules

Question 24

Basic components of immunoassays:

Answer 24

Analyte
Antibodies specific for the analyte
A label/ detection system
A method to separate bound from free components (ex. washing)

Question 25

Competitive immunoassays

Answer 25

the analyte and a tracer (labeled hormone) compete fofr limited amount of antibody
used for smaller analytes which can only bind one antibody at a time
the amount of tracer at the end is inversely proportional to the amount of analyte in the sample

Question 26

Noncompetitive (sandwich) immunoassays

Answer 26

all of the analyte binds a non-limiting concentration of antibody
no competition step
second antibody with tracer binds a distinct epitope on the analyte
used for larger analytes
the signal is directly proportional to the concentration of the analyte

Question 27

Common radioisotope

Answer 27

125I

Question 28

Fluorescent label

Answer 28

Eu (europium)

Question 29

Chemiluminescent label

Answer 29

acridinium ester

Question 30

Ruthenium particle:

Answer 30

chemiluminescence

Question 31

Colourimetry

Answer 31

a coloured complex generated when enzymes are incubated with the correct substrate

Question 32

Beads

Answer 32

gold, latex