Introduction to Endocrinology Flashcards
what is endocrinology?
endocrinology is the branch of physiology and medicine concerned with endocrine glands and hormones
what are endocrine glands
specialised organs that secrete chemical mediators (hormones) into the circulation
what do hormones do
they are a regulatory substance of cellular activity
act at sites remote from the site of production
target tissues / organs dictated by expression of receptors for the hormone
endocrine
act on remote tissues (main focus in clinical biochem)
autocrine
mediators act on the cell where they are produced
paracrine
mediators act on adjacent cells
hormone functions
homeostatic mechanisms in the body
energy production, utilisation and storage
growth and development
reproduction
many others
classification of hormoes
peptides e.g. oxytocin, ACTH, insulin, prolactin
glycoproteins - LH, FSH, TSH
amino-derived - thyroid hormones
steroids e.g. cortisol, testosterone, vit D
catechol (amines) - adrenaline and noradrenaline
others - fatty acid based hormones
mechanisms of proteins and amines hormone action
proteins and amines bind cell surface receptors, which in turn trigger intracellular secondary messenger systems which propagate the signal into and throughout a cell e.g. adrenaline
what are examples of intracellular messenger systems?
cyclic AMP
phospholipid systems
intracellular calcium
mechanisms of steroid hormone action
steroid hormones can diffuse directly into cells and bind intracellular receptors. the steroid-receptor complex then moves into the nucleus and activates or suppresses specific genes e.g. testosterone. protein hormones via a cell surface receptor can act very quickly (30s-2mins) but have shorter effects. steroid hormones can take hours to activate a response but by altering gene expression, steroids produce more long lasting effects
how are sets of endocrine glands usually organised?
into hierarchical loops that allow feed forward and feedback to regulate responses, these can be short or long loops. the vast majority of endocrine pathways are self limiting - incorporate some form of negative feedback loop
what are the 4 major endocrine pathways in clinical biochemistry?
hypothalamus - pituitary - adrenal (HPA) axis
hypothalamus - pituitary - gonadal axis
hypothalamus - pituitary - thyroid axis
anti diuretic hormone (ADH) - water balance
what is the hypothalamus
the hypothalamus is a key area of the brain involved in a wide range of homeostatic and metabolic processes. exerts many of its effects through stimulation of the pituitary gland. stimulated the anterior pituitary using peptides carried by capillaries. stimulates the posterior pituitary using neuronal signals
anterior pituitary hormones
adrenocorticotrophic hormone (ACTH) = multiple effects
growth hormone (GH)
follicle stimulating hormone
luteinising hormone
prolactin
thyroid stimulating hormone
