classes of hormones

Question 1

name the hormone classes.

Answer 1

• peptides
• amines
• iodothyronines
• cholesterol deriveratives and steroids

Question 2

what is meant by endocrine, paracrine and autocrine?

Answer 2

Endocrine – blood-borne, acting at distant sites

Paracrine – acting on adjacent cells

Autocrine – feedback on same cell that secreted hormone

Question 3

peptide hormones

Answer 3

Vary in length

Linear or ring structures

Two chains and may bind to carbohydrates

Stored in secretory granules, hydrophilic, water soluble

Released in pulses or bursts

Cleared by tissue or circulating enzymes

Question 4

iodothyronine hormones

Answer 4

not water soluble; 99% is protein bound

Only 20% of T3 in the circulation is secreted directly by thyroid

Secretory cells release thyroglobulin into colloid – acts as base for thyroid hormone synthesis

Incorporation of iodine on tyrosine molecules to form iodothyrosines

Conjugation of iodothyrosines gives rise to T3 and T4 and stored in colloid bound to thyroglobulin

TSH stimulates the movement of colloid into secretory cell, T4 and T3 cleaved from thyroglobulin

Question 5

synergism vs antagonism

Answer 5

Synergism – combined effects of two hormones amplified (glucagon with epinephrine)

Antagonism - one hormone opposes other hormone (glucagon antagonizes insulin)

Question 6

peptide, protein and steroid hormones

Answer 6

peptide:
short amino acid chains
eg insulin
hydrophillic
cannot cross membrane so bind to surface

protein:
long amino acid chains
eg growth hormone
hydrophillic
cannot cross membrane so bind to surface

steroid:
derived from cholesterol
lipid soluble
cortisol / sex hormones
easily cross membranes