An Introduction to the Endocrine System * Flashcards
what is endocrinology?
study of hormones
what is a hormone?
a substance secreted directly into the blood by specialised cells
what do hormones do in the body?
- Are present in only minute concentrations in the blood
- Bind to specific receptors in target cells to influence cellular reactions
what are the 6 terms used to refer to different ways that hormones are secreted? (JAPINE)
J - juxtacrine
A - autocrine
P - paracrine
I - intracrine
N - neuroendocrine
E - endocrine
what is endocrine?
secretes hormone directly into bloodstream which then acts on a distant target tissue.
what is intracrine?
cell synthesise its own hormone which then acts within the cell (hormone does not leave the cell)
what is autocrine?
The hormone leaves the cell and then docks back onto the same cell via its receptors
what is paracrine?
acts on nearby cells within the same tissue or organ
what is juxtacrine?
secreted hormone acts on neighbouring cells
what is neuroendocrine?
An electrical stimulus passes down a neurone (usually in the brain e.g. Hypothalamus) to a specialised cell causing it to secrete a hormone which will affect a distant target cell
what are the 2 different types of hormones?
steroid hormones
peptide hormones
what are steroid hormones?
fat soluble (and hydrophobic) meaning they can cross the phospholipid bilayer to bind to receptors in the cytoplasm which are usually transcription factors.
Once activated they travel to the cell nucleus and activate or inhibit transcription of a protein.
what are peptide hormones?
hydrophilic- need to bind to receptors on protein channels
Receptors undergo a conformational change moving the hormone across the plasma membrane into the cell to initiate a response.
what are the 6 ways in which hormones are regulated? (bob sold chris really hot peppers)
(BOB) Biosynthesis
(SOLD) Secretion
(CHRIS) Circulation/distribution
(REALLY) Receptor interaction
(HOT) Hormone metabolism/excretion
(PEPPERS) Peripheral modification
give an example of faulty biosynthesis?
Congenital adrenal hyperplasia- mutations in genes that code for enzymes involved in making steroid hormones in the adrenal glands
–> ambiguous genitalia
give an example of faulty secretion?
Congenital hypothyroidism - Thyroid gland is undeveloped so unable to secret the correct hormones or enough hormones.
give an example of faulty modification?
5-alpha reductase deficiency - Testosterone is a pre-hormone, it needs 5-alpha reductase to form to 5-alpha Dihydrotestosterone (final hormone). Leads to ambiguous genitalia, or female appearance
give an example of faulty receptors?
Androgen Insensitivity Syndrome- X-linked condition, Caused by faulty androgen receptor
Because there is so much testosterone (produced by Gonads) the body is able to convert it to oestrogen further exemplifying female characteristics e.g. breast development.
How to measure hormones?
Bioassays
Immunoassays
Mass spectrometry
Bioassays or immunoassays is where the hormone is bound to an antibody that is linked to a signal e.g. fluorescence. Measuring the fluorescence or frequency of signals shows the measurement of the hormones present
MS is more accurate method of measuring hormones
where is the pituitary located?
what are the main anterior and posterior pituitary hormones?
located in Sella turcica
Anterior pituitary hormones
ACTH - Regulation of adrenal cortex hormones
TSH - Thyroid hormone regulation
Growth hormone- Regulates Growth (+), metabolism
LH/FSH - Reproductive control and puberty
(PRL) Prolactin - Breast milk production
Posterior pituitary hormones
ADH - Water regulation
Oxytocin - Breast milk expression (lactation)
how does a hormone negative feedback loop work?
give example
e.g thyroid gland
name and explain the symptoms of 3 diseases that occur due to excess hormone production
WHEN GLANDS GO WRONG – EXCESS PRODUCTION
Grave’s disease (Hyperthyroidism)
Symptoms:
Bulging eyes
Thickening and reddening of the skin, especially on the shins and upper feet, Tiredness or muscle weakness, Trouble sleeping
Shaky hands
Rapid and irregular heartbeat
Weight loss without dieting
Cushing’s disease: Glucocorticoid excess
Symptoms:
increased fat on your chest and tummy, but slim arms and legs
buffalo hump: a build-up of fat on the back of your neck and shoulders
skin that bruises easily 🡪 large purple stretch marks
depression and mood swings
Acromegaly - Growth hormone excess, Due to pituitary tumour
Symptoms:
Increased frontal bossing
Enlargement of base of the nose
Thickening of the lips
Broad based fingers
name and explain the symptoms of 3 diseases that occur due to insufficient hormone production
WHEN GLANDS GO WRONG – TOO LITTLE PRODUCTION
Severe hypothyroidism
symptoms:
Fatigue
Dry skin
Hair loss
Weight gain
Puffy face
Enlarged thyroid gland (goiter)
Iodine deficiency goitre – due to lack of negative feedback which results in TSH excess
If iodine is deficient in the diet thyroid hormone can’t be produced.
As a result you get a low negative feedback
As a result you get excess TSH – which is a growth factor - tumour like growths on the neck near thyroid gland (goitre)
This is an example of TSH excess
Adrenal insufficiency (Addison’s disease) – ACTH excess
The adrenal gland is destroyed by auto antibodies
Disrupted feedback loop - due to cortisol deficiency, ACTH production is enhanced
Hyperpigmentation: of the skin
Large amounts of POMC is produced because it is required to produce ACTH.
Another product of POMC in this process is MSH => more MSH is produced.
MSH stimulates melanocyte cells activity in the skin which causes the skin to darken especially in Palmer crease (crease on palm).
Symptoms:
weight loss
lethargic
reduced stress response
more prone to infection
what general principles are used to manage hormone excess or deficiency?
If hormones are in excess
Remove the hormone gland
or
Block secretion/synthesis of hormone
If there is hormone deficiency
REPLACE the hormone e.g. injection of replacement hormone
