Overview hormones Flashcards
define a hormone
substance created directly into the blood stream (ductless) from endocrine gland
what gland secretes TSH and what does it do?
Thyroid-stimulating hormone released from ant. pituitary gland
Acts on thyroid gland (affects T4, T3)
What are the 3 types of intercellular messengers in the body
endocrine autocrine (secreted from and acts on same cell) paracrine (neighbouring cell target)
Explain the neuroendocrine messengers in the body
Stored in axon terminal. Hormones made are called neurohormones
neuroendocrine messenger, give 2 examples neurohormones and where they come from
oxytocin and arginine vasopressin (antidiuretic)
come from posterior pituitary gland
What are the 4 types of hormones? give example of each
Peptide hormone - TSH
Steroid hormone - cortisol
Derived from tyrosine - thyroid hormones
Eicosanoids - prostaglandins
peptide hormone synthesis. Explain the process of synthesis of peptide hormone starting from DNA
DNA - mRNA - protein (in cytosol) = preprohormone
Ribosomes - cleaves pre = prohormone
Golgi complex - processed and packaged = hormone
exocytosis upon arrival of stimulus
What’s a preprohormone?
What’s the pre- part?
precursor polypeptide
pre part means it is a signal peptide - saying it needs to be processed then secreted
Steroid hormone synthesis. Explain the entire process
no DNA involved
cholesterol as the precursor molecule - enzymatic conversion = lipophilic hormone (now can’t be stored)
hormone leaves via passive diffusion
What’s the starting point of steroid hormone synthesis?
cholesterol
DNA not involved – T/F?
TRUE
How does the hormone leave the cell? How does it move around the blood?
passive diffusion
isn’t dissolved in blood so can’t be moved easily
attached to a carrier protein to aid transport
what dictates the rate of steroid hormone and peptide hormone synthesis?
steroid - by how much is released
peptide - rate of exocytosis
between peptide and steroid hormones, which has the longer half-life and why?
What’s one special exception?
steroid and thyroid hormones have the longer half life and peptide hormones are prone to protein degradation
one special exception is if the hormone is bound?
what are the 2 receptor types for peptide hormones? How do peptide hormones cause action on the target cell?
G-protein coupled receptors (cause action via glucagon activating cAMP)
Tyrosine kinase linked receptor (e.g. insulin) cause action by releasing tyrosine kinase in cell
How do steroid hormones cause effect? What are the 2 receptor types?
binds to gene as a transcription factor to increase or decrease transcription of protein
cytosolic or nuclear receptor
what 3 things can metabolise hormones?
How are they excreted?
enzymes in liver, kidney, blood
excreted in urine and/or faeces
Explain negative and positive feedback
Negative feedback
– consequence negatively controls process (maintain a set-point)
Positive feedback
– consequence enhances or amplifies process further
what’s an endocrine axis?
series of endocrine glands, where hormones affects the other glands in the series
How can neuroendocrine reflexes influence hormone synthesis?
input from higher centres - can influence the endocrine
what’s the diurnal pattern of hormone secretion and give an example
Levels of cortisol spike as you wake. During the course of day, cortisol is used up. Trials and tribulations of waking day require cortisol
As you go on, in evening, a little more is produced to get through the day. In the night, you make more to ‘prep it in advance’ for the next day
Important for sampling blood for hormone patterns
summary - cortisol - peak in early morning, trough in late evening
what are the 3 types of hormone disorders?
- hormone excess (tumour or immunological = Graves’ disease)
- lack of hormone (genetic, immunological attack, surgical removal)
- decrease target-cell responsiveness
Distinguish between a primary and secondary defect
primary - associated with endocrine gland that makes the hormone
secondary - associated with anterior pituitary level at endocrine axis
how would you test for hyper and hyposecretion?
hyper- suppression test (failure to suppress indicates autonomous secretion)
hypo - stimulation test (failure to stimulate confirms)
what role does imaging play in diagnosing endocrine disorders?
many endocrine disorders are due to a presence of a tumour