Week 5 Endocrinology Intro Flashcards by Hamish Reed-Embleton

What is the difference between and endocrine and exocrine gland?

Endocrine glands:

Do not have ducts, products are secreted directly into blood:
e.g. pituitary, thyroid, adrenal, parathyroid glands, gonads (testis & ovaries)

Exocrine glands:

Products secreted via ducts to epithelial surfaces inside or outside the body:
e.g. sweat, salivary, mucus, mammary gastric, prostate glands, liver bile duct

Some glands, e.g. pancreas, do both:
Endocrine:
insulin, glucagon, somatostatin & pancreatic polypeptide
Exocrine:
digestive enzymes secreted via pancreatic duct to the small intestine

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What are the two types of endocrine signalling?

‘Classical’ endocrine signalling:
hormone carried by blood
to receptors on ‘target’ cells

Intracrine signalling:
inactive prohormone enters a cell
activated intracellularly
(e.g. sex steroids)

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A hormone which is an example of classical endocrine signalling?

Thyroxine

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A hormone which is an example of intracrine signalling?

Testosterone/ Oestrogen

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What are the two subtypes of endrocrine signalling where hormones diffuse straight through fluid in tissues rather than the blood?

Paracrine (local) signalling:
hormone diffuses through tissue fluids …
to receptors on ‘target’ cells

Autocrine (local) signalling:
hormone diffuses through tissue fluids …
to receptors on the same cell

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Difference between peptide, steroid and amine hormones?

Peptide hormones are peptides and are water soluable

Amine hormones bind to plasma proteins

Steroid protiens also bind to plasma proteins but contain a cholesterol backbone and can pass through the lipid membrane of a cell

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Give an example of a steroid hormone?

Testosterone and Oestrogen

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Give two examples of amine hormones

Adrenaline and thyroxine

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Give an example of a peptide hormone

Adrenocorticotropic hormone (ACTH)

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What is the diffuse endrocrine system?

Anything that has something to do with hormones that isn’t either the HP axis or the classic endocrine organs which interact with the HP axis

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Signalling hormones or End Organ hormones - which has a shorter half life?

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

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Where are hormones broken down?

Broken down int he liver and kidneys

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How does metabolism affect hormone levels?

The rate at which hormones are broken down is dependent on metabolism

If metabolism is increased then hormones go down and they are broken down faster

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What is the main interface between the central nervous system and the endocrine system?

Hypothalamus

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What is the difference in the way that the anterior and posterior pituitrary recieve signals?

The anterior pituriary recieves signals via hormones in the portal system from the hypothalamus

The posterior has a direct neural connection with the thalamus

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Complete this statement about the anterior pituitrary cells and corresponding hypothalamic releasing hormones

CRH: Corticotropin-releasing hormone
GNRH: Gonadotrophin releasing hormone
TRH: Thyrotropin-releasing hormone
DA: Dopamine
GHRH: Growth hormone-releasing hormone

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Complete this statement about the anterior pituitrary cells and corresponding hypothalamic releasing hormones

CRH: Corticotropin-releasing hormone
GNRH: Gonadotrophin releasing hormone
TRH: Thyrotropin-releasing hormone
DA: Dopamine
GHRH: Growth hormone-releasing hormone

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Complete this statement about which anterior pituitary hormones are released by which cells

ACTH: Adrenocorticotropic hormone
TSH: Thyroid stimulating hormone
FSH&LH: Follicle stimulating hormone & Luteinising hormone
GH (somatotrophin): Growth hormone
PRL: Prolactin

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Complete this statement about which anterior pituitary hormones are released by which cells

ACTH: Adrenocorticotropic hormone
TSH: Thyroid stimulating hormone
FSH&LH: Follicle stimulating hormone & Luteinising hormone
GH (somatotrophin): Growth hormone
PRL: Prolactin

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What two hormones are made in the posterior pituitary?

Oxytocin and Vasopressin

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Fill in the target organs and corresponding physiological or hormonal resonse

Describe the general levels of aterior pituitary hormone and target gland hormone you would see with a hormone producing tumour in the target gland

Describe the general levels of aterior pituitary hormone and target gland hormone you would see with a hormone producing tumour in the anterior pituitary

Describe the general levels of aterior pituitary hormone and target gland hormone you would see with target gland failure

Describe the general levels of aterior pituitary hormone and target gland hormone you would see with anterior pituitary failure

Which is these statements applies to Hypothalamic hormones, Pituitary hormones or Target tissue hormones: Hormones rarely measured in plasma (measure by petrosal sinus sampling) Hormones often measured in plasma for diagnosis Hormones measured in plasma for diagnosis AND to monitor hormone reduction or replacement

Hormones rarely measured in plasma (measure by petrosal sinus sampling) - Hypothalamic hormones Hormones often measured in plasma for diagnosis - pituitary hormones Hormones measured in plasma for diagnosis AND to monitor hormone reduction or replacement - target tissue hormones

What are steroid hormones made from?

Cholesterol

What is the key concept for how steroids are made?

Cholesterol side groups are cleaved or modified. The hydrophobic 6 carbon side chain is removed making steroid hormones more water soluble than cholesterol

What are the 6 main endogenous steroid hormone's we have to know about

Aldosterone Cortisol Androstenedione Progesterone Testosterone Oestrogen

Out of these 6 steroid hormones which ones are adrenal and which are gonadal: Aldosterone Testosterone Androstenedione Progesterone Cortisol Oestrogen

Adrenal: Aldosterone Cortisol Androstenedione Gonadal: Progesterone Testosterone Oestrogen

What is an axample of a mineralocorticoid?

Aldosterone Regulates sodium/potassium

What is an example of a glucocortcoid?

Cortisol glucose synthesis protein & lipid metabolism inflammation, immune response

What is an example of an adrenal androgen?

Androstenedione Fetal steroids & growth

What is the group of enzymes involved in the cleaving or modifying cholesterol side groups during steroidgenesis?

cytochrome P450s Clue P45 is what you get when you leave a job, so cholesterol gets this when it leaves being cholesterol

What does cholesterol side chain cleavage enzyme do?

P450scc converts cholesterol into pregnenolone which is the first step in steroidgenesis

What type of enzyme is involved in interconverting steroid from active to inactive form?

Steroid dehydrogenases/reductases They come in pairs and convert steroid form active forms to inactive forms

What is the purpose of inactivating hormones or binding the active ones to plasma proteins?

It saves them for the target tissues. Bound + inactive hormones are transported in the plasma hormones are re-activated in target tissues

Adosterone has a classical genomic steroid mechanism but also has a non-genomic mechanism mimicing that of a peptide or amine hormone. What are these functions?

Kindneys: Slow action (>30 mins-48hr) Aldosterone-regulated synthesis of kidney epithelial sodium channel (ENaC) subunits Rapid signalling (< 1 min) Aldosterone-mediated vasoconstriction of vascular smooth muscle & endothelial cells

What are the two structures of the adrenal glands?

Cortex: 80-90% of normal gland Make steroid hormones: Mineralocorticoids Glucocorticoids adrenal androgens Medulla: 10-20% of normal gland Make catecholamines: adrenaline (epinephrine) noradrenaline (norepinephrine)

What part of the adrenal gland is involved in the hypothalamic-pituitary-adrenal (HPA) axis

Adrenal cortex, specifically the zona fasciculata and zona reticularis as it is cortisol and androstenedione that is released in response to ACTH

The adrenal cortex can be subdivided into what? What do each of these parts make?

zona glomerulosa (ZG) - mineralocorticoids zona fasciculata (ZF) - glucocorticoids zona reticularis (ZR) - adrenal androgens

In a diurnal circadian rythym when is ACTH highest and when is Cortisol highest?

Diurnal CRH release regulates ACTH release: high in the early morning (04.00-08.00) lower later in the day ACTH regulates cortisol synthesis: High on waking (06.00-10.00) lower later in the day (with ‘stress’ activity spikes) lowest in the middle of the night

Metabolically how does the action of cortisol oppose that of insulin?

Generally speaking it opposes the action of insulin Anabolic: Increased gluconeogenesis & liver glucose output Catabolic: Inhibition of glucose uptake by peripheral muscle & fat tissue Immune system suppression Increased muscle protein breakdown Increased fat breakdown Increased bone resorption Increased appetite & central fat deposition

How is androstenedione converted in oestrogen and testosterone?

Intracrine conversion to testosterone & oestradiol in peripheral tissues

What are the main roles of Dehydroepiandrosterone (this is whats is actually made in the ZR and androstenedione is an intermediary to the final androgens)

Regulates secondary sexual characteristics: * **Facial & body hair, pelvic build, upper body musculature, body fat composition, etc.** Prenatal DHEA production: * **Role in maintaining oestrogenic environment** * Role in foetal development?? Postnatal DHEA production: * Role in initiation of puberty (adrenarche)?? * **Main source of androgens & post-menopausal oestrogen in females** * Role in longevity; elixir of life??

In the gonadal hormone feeback loop what is the extra hormone that inhibits the hypothalamus and pituitary ?

Inhibin

What is desmopressin?

A synthetic vassopressin

What is urine osmolality?

The concentration of chemicals in urine.

What another name for anti-diuretic hormone?

Vasopressin