Introduction to Endocrinology Flashcards
Endocrine vs Exocrine
Without ducts - Endocrine
With ducts - Exocrine
Define paracrine action
Acts on adjacent cells
Define Autocrine
Substances released by the cell will act on that cell
Difference in transport of water soluble and fat soluble hormones
Unbound - Water
Bound - fat
Difference in cell interaction of water soluble and fat soluble hormones
Water - bind to surface receptor
Fat - Diffuse into cell
Difference in Half-life of water soluble and fat soluble hormones
Water - short
Fat - long
Difference in clearance of water soluble and fat soluble hormones
Water - Fast
Fat - slow
Where are peptides stored
Vesicles
Are steroids stored
No, they are synthesised on demand
What two structures do peptides come in
Linear or ringed
How many chains do peptide hormones have
2
Three characteristics of peptides
Stored in secretory granules
Hydrophilic
Water soluble
What form are peptide hormones synthesised as
Preprohormone -> prohormone (cleaved) at ribosomes
Packaged: Prohormone -> hormone
Released: hormone
What kind of hormone are amines
Water souble
Where are amine derived from
Phenylalanine
Describe the path of production of epinephrine
L-phenylalanine -> L-tyrosine -> L-DOPA -> DOPAMINE -> Norephinephrine -> Epinepherine
How does epinephrine act on receptors
Binds to alpha-adrenoceptor :
- Receptor linked to Gq
- IP3 produced
What are thyroid hormones bound to
Albumin
What proportion of T3 in circulation is secreted directly by thyroid
20%
Property of vitamin D
Fat-Soluble
Describe the production of vitamin D
7-dehydrocholesterol -> Cholecalciferol -> Unfinished
Describe steroid action
- Steroid diffuses into cell
- Receptor-hormone complex forms
- Complex bins to GRE
- Transcription of gene to mRNA
What is basal secretion of hormones
Continuous or pulsatile secretion by cells
What is the rhythmic secretion of hormones
The amount of hormone secreted depends on the time of day (GH and TSH)
Role of inhibiting factors in steroid secretion
Increased secretion of one hormone inhibits secretion of another
Define synergism
Combined effects of two hormones amplified
Define antagonism
One hormone opposes another
What is hormone receptor induction
Induction of LH receptors by FSH
What is hormone down-regulation
Hormone secreted in large quantities causes down regulation of its target receptors
Where are hormones produced in the posterior pituitary gland
Hypothalamus by the paraventricular nucleus OR supraoptic nucleus
What is the blood supply to the posterior pituitary gland
Inferior hypophyseal artery
Where are hormones released by the posterior pituitary gland stored
Axon terminals
What stimuli causes increased vasopressin secretion
When blood volume falls (e.g. during shock )
What is oxytocin responsible for
Uterine contractions
What simulates oxytocin release other than labour
Suckling by myoepithelial cells
What simulates oxytocin release other than labour
Suckling by myoepithelial cells
Signs of a pituitary dysfunction
Tumour mass effects (will compress surrounding structures like the third, fourth and sixth cranial nerves which control eye movement and fifth which controls eye sensation)
Excess blood hormone levels
Hormone deficiency
Where is GH produced
Anterior pituitary gland
What does GH act on
Causes release of IGFs
Fat metabolism
Carbohydrate metabolism
Increased protein synthesis
What stimulates release of GH
GNRH released by the hypothalamus
Where is TRH produced
Hypothalamus
What does TRH do
Causes secretion of TSH from the anterior pituitary gland
Functions of the thyroid hormones
- Accelerates food metabolism
- Increases protein synthesis
- Stimulates carb metabolism
- Increases fat metabolism
- Increase Ventilation rate
- Increase CO and HR
- Growth rate accelerated
- Brain development during foetal life
What is the half life of T4
5-7 days
Half life of T3
1 day
What happens to T4 in the periphery sites
Converted to T3 which then activates the nucleus (most active form)
What causes release of ACTH
CRH b the hypothalamus
What does ACTH act on
Adrenal glands tor please Cortisol
Where in the adrenal gland is cortisol secreted from
Zona fasciculata
What is secreted from the Zona glomerulosa
Aldosterone
What is secreted from the Zona reticularis
Androstenedione
DHEA
Describe the Renin-angiotensin system
Check book
What is secreted by the adrenal medulla
Adrenaline
