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Endocrinolgy > Basic priciples and some histology > Flashcards

Basic priciples and some histology Flashcards

1
Q

Define what an endocrine gland does

A

Endocrine glands secrete hormones directly into the circulation

(Exocrine glands secrete via a duct to areas ‘without the body’

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2
Q

Definition of a hormone

A

“a chemical substance which is secreted without benefit of a duct, directly into the blood stream and which acts at long range, often slowly, on distant organs or tissues”

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3
Q

What are the types of actions of hormones?

A

Endocrine, neuroendocrine, paraendocrine, neurocrine, autocrine

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4
Q

Name 3 hormones which are tyrosine derivatives

A

Dopamine, adrenaline, thyroxine (T4)

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5
Q

Name 4 peptide hormones

A

small: thyrotropin releasing hormone (TRH) (3aa’s)
medium: adrenocorticotropic hormone (ACTH) (39aa’s)
large: prolactin (198aa’s)
2 chains linked by disulphide bridge - insulin (51aa’s)

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6
Q

4 Glycoprotien Hormones

A

luteinizing hormone (LH), follicle stimulating hormone (FSH) thyroid stimulating hormone (TSH), human chorionic gonadotrophin (hCG)
Alpha chain - species specific
Beta chain - hormone specific

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7
Q

What do mineralocorticoid steroid hormones affect?

Name one

A

affect water & electrolyte balance

Aldosterone

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8
Q

What do glucocorticoid steroid hormones affect?

Name one

A

affect carbohydrate & protein metabolism

Cortisol

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9
Q

What are the three sex steroid hormones

A

Oestrogen, testosterone, progesterone

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10
Q

What are the hormones of the anterior pituitary?

A

ACTH, GH, prolactin, FSH, LH, TSH

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11
Q

What are the hormones of the posterior pituitary?

A

ADH, oxytocin

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12
Q

What are the hormones of the hypothalamus?

A

TRH, CRH, GHRH, GnRH, somatostatin

Dopamine (median eminence)

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13
Q

How are Catecholamines formed and in what form do they my circulate?

A

Multi‐enzyme biosynthesis

Circulate in free form

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14
Q

How are thyroid hormones formed and in what form do they circulate?

A

Formed within thyroglobulin

Circulate mainly in bound form

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15
Q

How are proteins/ peptides formed and in what form do they circulate?

A

Rough endoplasmic reticulum
Peptides as precursor molecules
Circulate largely in free form

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16
Q

How are steroid hormones formed and in what form do they circulate?

A

Smooth endoplasmic reticulum
Formed form chlolesterol, multi‐enzyme biosynthesis
Circulate mainly in bound form

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17
Q

How are catecholamines and peptide hormones stored and released?

A

Catecholamines stored in SECRETORY GRANULE or VESICLE
Peptide hormones stored in SECRETORY GRANULE
both released by EXOCYTOSIS triggered by Ca2+
contents released and granule recycled contents released and granule recycled

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18
Q

How are thyroid hormones stored?

A

Thyroid hormones are stored in colloid as part of thyroglobulin

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19
Q

How are steroid hormones stored and released?

A

not stored, made from cholesterol stored in lipid droplets biosynthesis involves mitochondria & smooth endoplasmic reticulum
release not well understood

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20
Q

How do Catecholamines and peptide hormones bind in plasma?

A

They are largely hydrophilic and do not associate with plasma protein

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21
Q

How do Steroid hormones & thyroid hormones bind in plasma?

A

They are lipophilic and are highly bound to plasma proteins. Free i.e. non‐bound hormone is biologically active

22
Q

In plasma, what percentages of T4 are free, bound to thyroxine binding globulin (TGB), bound to pre‐albumin and bound to albumin?

A

0.04%
70%
20%
10%

23
Q

What percentages of testosterone are free, bound to corticosteroid binding globulin, bound to sex hormone binding globulin, bound to albumin?

A

2%
3%
60%
25%

24
Q

Methods of determining hormone levels

A

Bioassay, radioimmunoassay, Enzyme‐linked immunosorbant assay (ELISA)

25
Q

Actions of GH?

A

Growth of long bones until fusion of epiphyses, Increase in size of viscera, Anti-insulin effects
Metabolic effects related to growth: anabolic for protein catabolic for fats and carbohydrates
- via GH receptors and IGF production in the liver

26
Q

What are the treatments for acromegaly?

A

bromocriptine - D2 agonist - (in acromegaly cells develop D2 receptors)

octreotride - long acting somatostatin analogue

27
Q

Hat are the treatments for GH deficiency/small stature?

A

Treat with recombinant hGH (somatropin) or recombinant hIGF-1 (mecasermin)

28
Q

How do you test for GH function?

A

GH stimulation test: Fast for 12 hours then give insulin or arginine should cause increase in GH secretion should cause increase in GH secretion. GH suppression test: Fast for 12 hours then give glucose drink should suppress GH secretion
Measure GH or IGF1 to detect gigantism or acromegaly

29
Q

How can you test anterior pituitary function?

A

Hypothalamic releasing hormones e.g. Protirelin (synthetic TRH), GnRH, sermorelin (GHRH analogue).
Drugs influencing negative feedback e.g. dexamethasone (ACTH) clomiphene (LH)

30
Q

What are the types of vasopressin receptor and how do they work?

A

V1a - phospholipase C (PLC): blood vessels - vasoconstriction
V1b (V3) - phospholipase C (PLC): corticotrophs - increase ACTH release
V2 - adenyl cyclase: distal tubule, collecting duct - insert aquaporins, increase H2O permeability

31
Q

What do you know about Syndrome of inappropriate anti-diuretic hormone secretion (SIADH).

A

ADH Hypersecretion: normally secretion stops at a plasma osmolarity <275mOsmol/kg.

  • fluid retension, hyponatraemia
  • seen with Oat cell carcinoma of lung - ectopic secretion
32
Q

Hypo-secretion of ADH?

A
  • Diabetes insipidus
    Central (neurogenic)
    Peripheral (nephrogenic)
33
Q

Treatments for Syndrome of inappropriate anti-diuretic hormone secretion (SIADH)?

A

Demeclocycline (a tetracycline) - Disrupts AHD signalling

Conivaptan - V1a/V2 receptor antagonist

Tolvaptan - V2 receptor antagonist

34
Q

What is the treatment for diabetes insidious?

A

Treatment desmopressin – selective V2 agonist given as nasal spray

35
Q

Briefly describe the anatomy of the thyroid

A
  • 2 pear-shaped lateral lobes connected by a midline isthmus
  • intimately related to the trachea
  • isthmus lies at level of 2nd-4th tracheal rings
  • isthmus may be joined to the hyoid bone by a fibrous cord, a remnant of the embryological thyroglossal duct.

Development

• Arises from a diverticulum in floor of the primitive h j t d l t th

Week 4, in utero

pharynx just caudal to the site of the future tongue

– thyroglossal duct

– opens at base of tongue as

Week 6, in utero

p g the foramen caecum

– connection to pharynx eventually lost, isolating the gland

More, K.L.

Cellular organization

• Thyroid epithelial cells are organized into

Wheater’s Functional Histology

organized into follicles. – secrete thyroglobulin (large glycoprotein, mw 660Kd) – accumulates in the follicles as “colloid”

36
Q

What the developmental origins of the thyroid?

A

Arises from a diverticulum in floor of the primitive pharynx just caudal to the site of the future tongue
– thyroglossal duct
– opens at base of tongue as the foramen caecum
– connection to pharynx eventually lost, isolating the gland

37
Q

How are the cells of the thyroid organised?

A

• Thyroid epithelial cells are organized into follicles.

– secrete thyroglobulin (large glycoprotein, mw 660Kd) – accumulates in the follicles as “colloid”

38
Q

By what mechanism do thyroid cells produced and secrete T3 and 4?

A

Thyroid follicular cells take up iodide which is then oxidized to Iodine and covalently attached to the tyrosines of thyroglobulin.
• On stimulation by TSH (from the anterior pituitary) follicular cells endocytose the iodinated thyroglobulin and break it down in lysosomes. They release thyroxine (T4) or tri-iodothyronine (T3).

39
Q

What are C cells/Parafollicular cells?

A

scattered cells found within the follicular epithelium or as clusters between the follicles.
• larger, more rounded than the follicle cells
• secrete calcitonin (inhibits Ca++ mobilization) • neural crest-derived - migrate to thyroid during development.

40
Q

What is the minor cell type in the parathyroid glands and what do they do?

A

There is a second, minor population of population of larger, eosinophilic oxyphil cells, of unknown function (lack secretory granules).

41
Q

Briefly describe the anatomy of the adrenal gland

A

• Pyramidal (right) or crescent-shaped (left)
- bodies in contact with the upper poles of the kidneys
Separated from
• Separated from kidneys by connective tissue but surrounded by the renal fascia.

42
Q

What are the developmental origins of the adrenal cortex and adrenal medulla?

A

The adrenal glands have 2 distinct parts with different origins:
• Cortex – derived from the coelomic epithelium (mesothelium) lining the posterior abdominal wall wall
• Medulla – derived from an adjacent sympathetic ganglion

43
Q

What type of hormones does the adrenal cortex secrete and what are the 3 regions of it?

A

• Cells secrete steroids

Cells are organized into 3 zones:-– Zona glomerulosa – Zona fasciculata – Zona reticularis

44
Q

What is the organisation and the role of the zona glomerulus and how is it regulated?

A
  • cells are arranged in clusters surrounded by capillaries.
  • secrete mineralcorticoids - mainly aldosterone - 95%
  • Target - Na+ retention in the kidney - d.c.tubule
  • regulated by the renin/angiotensin system
45
Q

What is the organisation and the role of the zona fasciculata and how is it regulated?

A

cells arranged in straight cords, running radially
• secrete glucocorticoids – mainly cortisol (95%)
• Target : glucose, lipid and protein metabolism
• secretion regulated by ACTH

46
Q

What is the organisation and the role of the zona reticularis and how is it regulated?

A
  • cells arranged in irregular cords
  • secrete some glucocorticoids and small quantities of sex steroids (mostly weak androgens)
  • functionally insignificant (?)
47
Q

Briefly describe the anatomy of the parathyroid glands

A

• 2 pairs of parathyroid glands, each about the size of a pea
Usually found on or embedded in the posterior border of the lateral lobes of the thyroid gland, but position is somewhat variable (esp. inferior parathyroids) parathyroids)
No functional significance in the association between thyroid and parathyroid glands

48
Q

What cells are found in the adrenal medulla?

A

Chomaffin cells
modified sympathetic ganglion
• large, polyhedral cells arranged in clumps or cords
• resemble “axon-less” ganglion

49
Q

What is the mechanism for secretion from the adrenal medulla and what is secreted?

A 
receive a (cholinergic) preganglionic sympathetic input from the greater and lesser splanchnic nerves, via the coeliac ganglion. 
• on stimulation, secrete catecholamines directly into the blood 
• 80% of the cells secrete adrenaline (epinephrine); the rest, noradrenalin (norepinephrine) The high concentration of glucocorticoids from g the cortex is needed to induce the enzyme responsible for converting noradrenalin to noradrenalin to adrenalin.
50
Q

What are the islets of langerhans?

A

Small, rounded clusters of cells, 100-200 micrometers in diameter embedded within the exocrine pancreas
• The cells are smaller and more-lightly stained than the exocrine cells, and arranged in irregular cords around capillaries.

51
Q

What are the cell types of the pancreas?

A

Using immunocytochemistry, 4 main cell types can be distinguished:
• A or  cells (~20%) secrete glucagon
• B or  cells (~70%) secrete insulin
• D or  cells (5-10%) secrete somatostatin
• F or PP cells (1-2%) secrete pancreatic polypeptide p yp p
• Other, minor cell types secrete vasoactive-intestinal peptide (VIP), substance P, motilin, serotonin, etc.

52
Q

What is the diffuse neuroendocrine system?

A

• Scattered cells found especially in the gut and respiratory system respiratory system
• Secrete amines or peptides with hormone-like or neurotransmitter activity
e g gastrin CCK secretin e.g. gastrin, CCK, secretin, enteroglucagon, serotonin etc
• Often secrete locally (paracrine)
• Cells often have ability to take up and decarboxylate amines

– Old name – APUD cells (amine precursor uptake and decarboxylation)
• Possess synaptic vesicle-like structures or neurosecretory-type granules (dense core granules)
– released by exocytosis in response to external stimuli

Endocrinolgy (8 decks)

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