Endocrinology Flashcards
What are the three ways hormones are distributed through?
Endocrine – blood-borne, acting at distant sites
Paracrine – acting on adjacent cells
Autocrine – feedback on same cell that secreted hormone
Features of water-soluble hormones
Transport - unbound
Cell interaction - bind to surface receptor
Half-life - short
Clearance - fast
Features of fat-soluble hormones
Transport - protein bound
Cell interaction - diffuse into cells
Half-life - long
Clearance - slow
What are the 4 classes of hormones?
- Peptides
- Amines
- Iodothyronines
- Cholesterol derivatives and steroids
What are the different mechanisms used to control hormone secretion?
Basal secretion – continuously or pulsatile
Superadded rhythms e.g day-night cycle – ACTH, prolactin, GH and TSH
Release inhibiting factors – dopamine inhibiting prolactin, sum of positive and negative effects (GHRH and somatostatin on GH)
Releasing factors
What hormones does the posterior pituitary synthesise?
NONE! Oxytocin and vasopressin (ADH) is stored in the posterior pituitary but is synthesised in the hypothalamus.
What would stimulate vasopressin release?
Vasopressin is an antidiuretic hormone. It is stimulated to absorb water from the kidney.
*Hypertonic concentration
*Loss of blood volume
*Stress
What does vasopressin do?
*Vasoconstricts blood vessels
*Increased release of aldosterone which leads to increased absorption of water
*Stimulates the release of ACH which in turn stimulates the release of cortisol
Where is oxytocin released?
Posterior pituitary gland
Function of oxytocin?
- Uterine contraction during labour.
- Milk ejection
What hormones are produced in the anterior pituitary gland and what are they stimulated by?
TSH - stimulated by TRH from hypothalamus
ACTH - stimulated by CRH from hypothalamus
FSH and LH - stimulated by GnRH from hypothalamus
GH - stimulated by GHRH from hypothalamus
PRL - inhibited by dopamine from hypothalamus
What are the three ways that someone with pituitary dysfunction would present?
*Tumour mass effects
*Hormone excess
*Hormone deficiency
What investigations should be conducted in patients with pituitary dysfunction?
- Make a clinical diagnosis
- Hormonal tests
- If hormonal tests abnormal or tumour mass effects perform MRI pituitary
When is oxytocin released?
It is stimulated by cervical dilation
Where does growth hormone act?
In the liver
What hormone does GH stimulate?
Insulin-like growth factors (IGFs)
Functions of thyroid hormone
*Accelerates food metabolism
*Increases protein synthesis
*Stimulation of carbohydrate metabolism
*Enhances fat metabolism
*Increase in ventilation rate
*Increase in cardiac output and heart rate
*Brain development during foetal life and postnatal development
*Growth rate accelerated
Main function of cortisol?
Major metabolic and stress hormone
Describe the structure of the adrenal gland.
Adrenal gland is divided into the medulla and cortex.
The cortex is made up of three layers:
GFR
*Zona glomerulosa
*Zona fasciculata
*Zona reticularis
Where in the adrenal cortex are mineralocorticoids produced and give an example of one.
Zona glomerulosa.| - Aldosterone.
Where in the adrenal cortex are glucocorticoids produced and give an example of one.
Zona fasciculata.| - Cortisol androgens
Where in the adrenal cortex are androgens produced and give an example of one.
Zona reticularis.| - androstenedione and DHEA
What is released by the adrenal medulla?
Epinephrine and norepinephrine
What happens in the zona glomerulosa
Renin-angiotensin system
*Low Na, sympathetic
*Renin acts on zona glomerulosa producing aldosterone
*Increases absorption of Na+ and increased K+ excretion
*Blood volume increases and/or BP