Endocrine system II
Friday, September 13, 2019 11:00 AM
Endocrine hormones fall into 3 major chemical classes:
Amine hormones -- derivatives of the amino acid tyrosine made by the thyroid
gland, adrenal medulla, and hypothalamus
**Pathway of epinephrine synthesis: tyrosine --> DOPA --> dopamine -->
norepinephrine --> epinephrine
i. Thyroid hormones
a. T3 and T4 -- require iodine to work
b. Produced by the thyroid gland
c. Goiter: a greatly enlarged thyroid gland that can result from iodine
deficiency
ii. Epinephrine and norepinephrine
iii. Dopamine
Note: ii and iii are catecholamines (derived from tyrosine)
Peptides and proteins -- make up most hormones
- E.g. insulin and glucagon (required for glucose homeostasis)
- Made as large, inactive preprohormones
○ Include a signal sequence, one or more copies of the hormone, and
additional peptide fragments
○ Insulin synthesis pathway: preproinsulin --> cleaved into proinsulin -->
insulin and C-peptide
§ C-peptide is used as a marker of insulin secretion
Peptide hormone synthesis and processing
1. Signal sequence of the preprohormone directs it into the lumen of the rough ER
2. Enzymes in the ER cut off the signal sequence, creating a prohormone
3. Prohormone passes from the ER to the Golgi complex
4. Secretory vesicles containing enzymes & prohormone bud off the Golgi
a. Chop off the prohormone into 1+ active peptides and additional
fragments
Friday, September 13, 2019 11:00 AM
Endocrine hormones fall into 3 major chemical classes:
Amine hormones -- derivatives of the amino acid tyrosine made by the thyroid
gland, adrenal medulla, and hypothalamus
**Pathway of epinephrine synthesis: tyrosine --> DOPA --> dopamine -->
norepinephrine --> epinephrine
i. Thyroid hormones
a. T3 and T4 -- require iodine to work
b. Produced by the thyroid gland
c. Goiter: a greatly enlarged thyroid gland that can result from iodine
deficiency
ii. Epinephrine and norepinephrine
iii. Dopamine
Note: ii and iii are catecholamines (derived from tyrosine)
Peptides and proteins -- make up most hormones
- E.g. insulin and glucagon (required for glucose homeostasis)
- Made as large, inactive preprohormones
○ Include a signal sequence, one or more copies of the hormone, and
additional peptide fragments
○ Insulin synthesis pathway: preproinsulin --> cleaved into proinsulin -->
insulin and C-peptide
§ C-peptide is used as a marker of insulin secretion
Peptide hormone synthesis and processing
1. Signal sequence of the preprohormone directs it into the lumen of the rough ER
2. Enzymes in the ER cut off the signal sequence, creating a prohormone
3. Prohormone passes from the ER to the Golgi complex
4. Secretory vesicles containing enzymes & prohormone bud off the Golgi
a. Chop off the prohormone into 1+ active peptides and additional
fragments
