Diabetes and Endocrinology Intro Flashcards
Define endocrine, paracrine, autocrine and exocrine
- Endocrine: Secretes into blood
- Paracrine: Secrete locally
- Autocrine: secretion acts on the same cell
- Exocrine: Secrete to the external environment via ducts
Define neuroendocrine secretion and give an example of where it occurs
- Nerves release hormones into the blood
- Hypothalamic - posterior pituitary axis
What are the principle endocrine glands?
- Hypothalamus and pituitary
- Thyroid and parathyroid
- Pancreas
- Adrenal glands and kidneys
Features of endocrine hormones?
- Secreted into blood
- Exert their effects at very low concentrations (10^-9 - 10^-12 M)
- Action often terminated by negative feedback loops
3 Types of endocrine hormones and what they’re derived from?
- Peptide hormones - composed of chains of AA’s
- Amine hormones - derived from one of two amino acids (tryptophan or tyrosine)
- Steroid hormones - derived from cholesterol
Describe the general synthesis and excretion process of peptide hormones such as TRH, FSH and Insulin
- Synthesized as preprohormone, directed through ER by signal sequence
- Signal sequence cut off by peptidases, becomes prohormone
- Prohormone moves from ER through Golgi
- Secretory vesicle containing peptidase and prohormone buds off golgi
- Peptidase chops prohormone into active hormone and secretes
Why is measuring C-Peptide useful clinically?
- Can be used to measure endogenous insulin production
(levels of C-Peptide usually about 5x higher bc insulin is metabolized faster
Why do peptides bind on the surface of cells?
What signalling pathways to they tend to work by?
- Bc they are water soluble for blood transport so can’t cross membrane
- Work via G protein coupled or tyrosine kinase linked receptor pathways
How do G protein Coupled Receptors work? Rate of response?
Same for Tyrosine Kinase Linked Receptors?
- GPCR: activates 2nd messenger or ion channels, leading to modification of existing proteins. Rapid response
TKLR: Alters gene expression when bound, slower response but longer lasting activity
Which AA are most amine hormones derived from?
Examples of these hormones?
- Tyrosine
Examples:
- Dopamine
- Norepinephrine
- Epinephrine
Which hormone is the only amine hormone that isn’t tyrosine derived? What is it derived from?
- Melatonin (regulates circadian rhythym)
- Tryptophan
Different types of tyrosine derived hormones? Difference?
- Catecholamines (hydrophilic)
2. Thyroid Hormones (lipophilic)
How are steroid hormones unlike the other hormones? Consequence of this?
- They very lipophilic
- Because of this they are synthesized as needed rather than made and stored, as their lipid solubility means they can’t be retained within membranes and diffuse into ISF & blood uncontrollably
Where are steroid hormones produced?
and the hormones produced by each location
- Gonads (testes and ovary): sex steroids
- Placenta: hCG, sex steroids
- Kidney: Vitamin D3
- Adrenal cortex: corticosteroids
Where are the receptors for steroid hormones located and why?
- Inside cells (cytoplasmic or nuclear receptors)
- Because steroid hormones are lipophilic and can cross cell membranes
