Flashcards in Endocrine Deck (270)
What is an endocrine hormone?
blood borne and acts at distant sites
What is a paracrine hormone?
acting on adjacent cells
What is an autocrine hormone?
feedback on the same cell that secreted the hormone
What is an endocrine gland?
secretes into the blood stream (thyroid, adrenal, beta cells of the pancreas)
What is an exocrine gland?
secretes through a duct (pancreas amylase and lipase)
Do fat soluble of water soluble hormones have a longer half life?
Are fat soluble of water soluble hormones protein bound or unbound?
fat - protein bound
water - unbound
Where do peptides store hormones?
in secretary granules
What are the different classes of hormones?
peptides, amines, idothyronines, cholesterol derivatives and steroids
Synthesis of T3 and T4?
thyroglobulin released into colloid and acts as a base for thyroid hormone sysnthesis, the incorporation of iodine forms idothyrosines, it is conjugated and then forms T3 and T4 and stored in colloid bound to thyroglobulinm TSH stimulates the movement of colloid unto secretory cell, T4 and T3 cleaved from thyroglobulin
How do adrenocortical and gonadal steroids work?
enter call and pass to nucleus by diffusing through plasma membrane, altered to an active metabolite and bind to a cytoplasmic receptor, receptor hormone complex binds to GRE, initiating transcription of gene to mRNA, and this directs protein synthesis
How is hormone secretion controlled?
continuous basal secretion, superadded rhythms (day night cycle), release inhibiting factors, releasing factors
What is synergism?
combined effects of two hormones amplified
What is permissiveness?
a hormone needed for another's full potential effect
Function of the 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
Function of growth hormone?
stimulates production of IGF-1 to induce metabolic changes
decreases adipose, increase liver function and increase muscle, increase protein synthesis, increase lipolysis
What hormone stimulates GH?
GHRH (grehlin increased GH secretion)
What hormone inhibits GH?
What is acromegaly?
an overgrowth of all organ systems, bones, joints, soft tissues from excessive GH secretion after fusion of the epiphyseal plates
What is giantism?
an overgrowth of all organ systems, bones, joints, soft tissues from excessive GH secretion before fusion of the epiphyseal plates
What causes acromegaly?
benign pituitary GH producing adenoma or GHRH producing bronchial carcinoid
Symptoms of acromegaly?
arthralgia, arthritis, bp raised, carpal tunnel syndrome, diabetes, enlarged organs, field defect
prognathism, interdental separation, macro glossia, spade like hands and feet, increased jaw and hand size, lower pitch of voice, headaches
Investigations for acromegaly?
monitor visual fields, raised glucose, serum phosphate, urinary calcium and serum triglycerides, MRI and CT, IGFBP-3 increased, ECG, ECHO, serum prolcatin, raised IGF-1
What is the diagnostic test for acromegaly?
glucose tolerance test
GH is inhibited by glucose so should be suppressed 2 hours after oral glucose load, if not
What is IGFBP-3?
the main binding protein for circulating IGF, and is increased in acromegaly due to increased IGF-1
Management of acromegaly?
control symptoms, normalise hormones levels and correc tumour compression
trans-sphenoidal surgery of endoscopic trans sphenoidal treatment in pituitary adenomas if non invasive macroadenoma
How does pegvisomant treat acromegaly?
for those who don't respond to somatostatin, suppressed IGF-1 levels - does not affect tumour size
How does somatostatin analogues treat acromegaly?
inhibit GH secretion
side effect of long term dopamine agonists for acromegaly?
cardiac fibrosis - need regualr ECHO