Endocrinology - Week 1 Flashcards Preview

Year 2 - Semester 2 > Endocrinology - Week 1 > Flashcards

Flashcards in Endocrinology - Week 1 Deck (107)
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what hormones does the pituitary release?

o ACTH (Adrenocorticotropic hormone)
o LH (Luteinising hormone)
o FSH (Follicle stimulating hormone)
o GH (Growth hormone)
o PRL (Prolactin)
o TSH (Thyroid stimulating hormone)
o AVP (Arginine vasopressin)


what hormones does the thyroid release?

o Thyroxine
o calcitonin


what hormones does the parathyroid release?



what hormones does the pancreas release?

o Insulin
o glucagon


what hormones does the adrenal cortex release?

o Cortisol
o Aldosterone


what hormones does the adrenal medulla release?

o Adrenaline
o Noradrenaline


what hormones do the testes release?

o Testosterone


what hormones do the ovaries release?

o Oestrogen
o Inhibin


what hormones does adipose tissue release?

o Leptin
o Adiponectin
o Resistin
o TNFa
o IL6
o Cortisol
o Angiotensinogen
o PAl-1


what types of hormones are there

• Peptides
o Growth hormone
o Insulin
o Thyroxine

• Amines
o Adrenaline
o Noradrenaline

• Steroids
o Oestrogen
o Androgen
o Glucocorticoids
o Vitamin D


what receptors do amines have

• Surface receptors
• Secondary messengers
• Multiple cellular effects


what receptors do steroids and thyroid hormones have

• Nuclear receptors
• Via transcription/translation
• Many gene targets


what does an excess of GH cause and what are the causes

o Acromegaly in adults
o Gigantism in children

o Causes
 Genetic – mutations in Gs-alpha
 Immune – antibodies stimulating GH
 Tumours – pituitary
 Overstimulation – GHRH hypersecretion
 Downstream path – IGF1 tumours
 Factitious/iatrogenic – body builders/ athletes


what to do if a hormone is in excess

show it can be suppressed back to normal


what to do if a hormone is deficient

replace it physiologically
• Diurnal rhythms make it hard to check hormone levels normally
• As do stress and illness


what makes up endocrine systems

at least three organs – one releases a signal, one secretes a hormone and the last responds to the hormone


what is the difference between endocrine and exocrine

Endocrine glands – do not have ducts and products secreted directly into the blood
Exocrine glands – have ducts to epithelial surfaces inside or outside the body
Some glands do both e.g. pancreas – endocrine such as insulin but also exocrine into the gut

“classical” endocrine signaling - hormone carried by blood to receptors on “target” cells


what are the three types of signalling other than endocrine

• Paracrine
o Hormone diffuses through tissue fluids
o To receptors on target cells

• Autocrine
o Hormone diffuses through tissue fluids
o To receptors on same cell

• Intracrine
o Inactive prohormone enters a cell
o Activated intracellularly
o E.g. sex steroids


describe peptide hormones

o Water soluble - circulate in blood
o Bind to surface receptors such as GPCRs or receptor kinases
o Fast acting

o Three types
• Hypothalamic-releasing hormone
• Pituitary trophic hormones
• Target organ peptide hormones


describe steroid hormones

o Transported on plasma “carrier” proteins
o Lipid soluble
o Diffuse through plasma membrane and bind to inactive cytoplasmic steroid receptors
o Activated “transcription factor” enters nucleus and binds to control regions activating gene transcription
o mRNA leaves the nucleus  new cytoplasmic protein synthesis
o this takes time – minimum 24-48 hours


describe amine hormones

o Transported on plasma “carrier” proteins
o Bind to surface receptors such as GPCRs or receptor kinases


describe the balance between hormone production and degradation

• Amplification:
‘Signalling’ hormones:
short half-life - only a few mins
‘End-organ’ hormones:
long-lived - hours to days

• Hormone levels in the blood
balanced between:
synthesis & secretion
degradation & excretion
• degraded mainly in liver & kidneys
• breakdown products excreted in urine, faeces and bile


what does the hypothalamus coordinate?

central neural inputs

External environment:

sight, sound, touch, taste, smell
pain, heat, cold , fear (‘freeze, fight or flight’)

Internal physiology:
blood pressure, osmolality, blood glucose
hypoglycaemia, starvation chronic pain, fever, inflammation

Circadian biological clock:
Suprachiasmatic nucleus (SCN) rhythm generator controls daily endocrine system cycles (entrained by daily light & dark cycle)

• Stimuli from somatic & visceral sense organs
• transmitted via sensory & motor neurons from the forebrain and mid brain
• produce ‘stimulatory’ or ‘inhibitory’ neurotransmitters
(dopamine, adrenaline, noradrenaline, serotonin, acetycholine & various neuropeptides)
• Act on distinct hypothalamic ‘nuclei’
stimulate production of hypothalamic-releasing hormones


describe hypothalamus

Neuroendocrine component of the nervous system within the brain
Located at the base of the brain
Linked via the pituitary stalk to the pituitary gland outside the brain


describe the pituitary gland

two glands in one:
Anterior and posterior pituitary have different embryological origins
• Anterior pituitary:
o blood supply from median eminence
• Posterior pituitary:
o Innervated by hypothalamic axons


whats important about the vasculature between the hypothalamus and the pituitary?

it is easily damaged which an lead to cranial diabetes insipidus etc


what hormones act on which cells in the anterior pituitary

• GHRH (somatoliberin) acts on Somatotrophs
• GnRH acts on Gonadotrophs
• CRH acts on Corticotrophs
• TRH acts on Thyrotrophs
• DA (dopamine), inhibits Lactotrophs
• Somatostasin (SS) inhibits Somatotrophs & Thyrotrophs


what happens in the posterior pituitary

• Oxytocin & Vasopressin stored and released in response to neural stimulation


what is released from the anterior pituitary?

• ACTH from Corticotrophs
• TSH from Thyrotrophs
• FSH & LH from Gonadotrophs
• GH (somatotrophin) from Somatotrophs
• PRL from Lactotrophs


describe HP axis feedback circuits

Stimulatory or inhibitory external neural inputs
Hypothalamic releasing-hormone acts on pituitary
Anterior pituitary hormone acts on target gland
Target gland hormone feeds back on Pit & Hyp
Feeds forward on tissue target/metabolism