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Endocrine System > The Endocrine System > Flashcards

The Endocrine System Flashcards

1
Q

What are the different components of the endocrine system?

A
  • Network of glands - secrete chemical messengers (hormones) into bloodstream
  • Hormones act on target cells
  • Regulation of metabolism, growth and development, tissue
  • Maintain functional balance
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2
Q

How is the balance of hormone maintained?

A

Negative feedback

• Build up of target organ secretory product after hormone binds inhibits hormone production

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3
Q

What glands and structures are part of the endocrine system?

A
  • Pineal gland
  • Hypothalamus
  • Pituitary
  • Thyroid gland
  • Parathyroid glands
  • Adrenal glands
  • Pancreas

Other organs - ovary, testes, kidney
Diffuse endocrine cells - lung, GIT

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4
Q

What occurs in endocrine diseases?

A

Disease processes lead to changes in function and/or structure

Dysregulated hormone release
• Hyperfunction
• Hypofunction

Effect of a MASS lesion

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5
Q

What disease processes occur in endocrine organs?

A
  • Hyperplasia (increased number and secretory activity of cells)
  • Atrophy (diminution of cells due to lack of stimulation)
  • Tissue damage (inflammation, autoimmune disease, compression, trauma, infarction)
  • Neoplasia (adenoma, carcinoma)
  • Congenital abnormality
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6
Q

What is the function of the thyroid gland?

A

Synthesis, storage and release of:
• Thyroxine (T4), triiodothyronine (T3) - regulate basal metabolic rate
• Calcitonin - regulates calcium homeostasis

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7
Q

Describe the histology of the thyroid gland

A
  • Follicles
  • Colloid-contains thyroglobulin
  • Epithelial cells – TG synthesis, iodination, resorption & release of T4 and T3
  • C-cells – secrete calcitonin (not visible)
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8
Q

Describe the hypothalamus-pituitary-thyroid axis

A
  1. Hypothalamus stimulates pituitary via TRH
  2. Pituitary stimulates thyroid via TSH

Negative feedback:
1. Thyroid T3 and T4 inhibits hormone release from pituitary and hypothalamus

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9
Q

Name manifestation of thyroid diseases

A
  • Hyperthyroidism - thyrotoxicosis
  • Hypothyroidism - myxoedema, cretinism, subclinical
  • Thyroid enlargement - goitre, isolated nodule/mass
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10
Q

Name thyroid diseases (mostly primary)

A
  • Thyroiditis
  • Gland destruction
  • Multinodular goitre
  • Tumours
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11
Q

Name three causes of hyperthyroidism

A
  • Diffuse toxic hyperplasia (graves disease)
  • Toxic multinodular goitre
  • Toxic adenoma
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12
Q

What occurs in Graves disease?

A

Autoimmune production of anti-TSH receptor antibodies
• Stimulate activity, growth, inhibit TSH binding
• Ophthalmopathy immune mediated - ocular fibroblasts have TSH receptor

Thyroid
• Diffuse hyperplasia and hyper function

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13
Q

Name four causes of hypothyroidism

A
  • Hashimoto’s thyroiditis (auto-immune destruction)
  • Iatrogenic - surgery drugs
  • Iodine deficiency
  • Congenital hypothyroidism
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14
Q

What is Hashimoto’s thyroiditis?

A

Autoimune destruction of thyroid epithelial cells
• Cytotoxic T cells, cytokine and antibody mediated destruction
• Circulating autoantibodies to
thyroglobulin ,
thyroid peroxidase

Thyroid
• Diffuse enlargement gradual failure

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15
Q

What is the histology in Hashimoto’s thyroiditis?

A
  • Hurthle cell change (thyroid cancer)

* Intense infiltrate of lymphocytes and plasma cells

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16
Q

What is goitre?

A

Enlarged thyroid

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17
Q

How does multi nodular goitre arise?

A
  1. Iodine deficiency due to goitrogens
  2. Impaired synthesis of T3, T4
  3. Increase TSH
  4. Hypertrophy and hyperplasia of epithelium
  5. Simple -> multi nodular
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18
Q

What are goitrogens?

A

Substances that disrupt the production of thyroid hormones by interfering with iodine uptake in the thyroid gland.

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19
Q

What is the histology of goitre?

A
  • Crowded follicles
  • Distended colloid filled follicles
  • Haemorrhage, fibrosis, cystic change
  • Nodular appearance
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20
Q

What investigations are used for thyroid nodules?

A

TFTs, ultrasound and FNA

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21
Q

What are different causes of a thyroid nodule?

A
  • Dominant nodule in multi nodular goitre
  • Cyst
  • Follicular adenoma
  • Carcinoma - differentiated thyroid carcinoma (papillary or follicular)
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22
Q

What is the use of cytology in thyroid nodules?

A
  • Diagnosis of solitary/dominant nodule
  • Solid, cystic
  • Reduce need for surgery
  • Clusters of follicular epithelial cells
  • Background colloid
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23
Q

Name different types of thyroid tumours

A

• Follicular adenoma

Carcinoma:
• Differentiated thyroid carcinoma (DTC) - papillary or follicular
• Anaplastic carcinoma
• Medullary carcinoma

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24
Q

Describe follicular adenoma

A
  • Most non-functioning
  • Circumscribed, encapsulated tumour
  • Histology often small microfollicles
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25
Q

Describe differentiated thyroid carcinoma - follicular carcinoma

A
  • Rare, usually solitary
  • Malignant cells breach capsule
  • Metastases - blood, bones

• RAS mutation or translocation

26
Q

Describe differentiated thyroid carcinoma - papillary carcinoma

A
  • Usually < 50yrs
  • BRAF mutation or RET/PTC gene rearrangement
  • Associated with exposure to ionising radiation
  • Spreads via lymphatics
  • Excellent prognosis (95% survival)
27
Q

Describe the histology of DTC - papillary carcinoma

A
  • Papillary projections
  • Empty nuclei
  • Psammoma bodies
  • May be cystic
28
Q

Describe thyroid medullary carcinoma

A
  • Malignant tumour of C cells
  • Produces calcitonin (+/- other polypeptides)
  • 70% sporadic
  • Prophylactic thyroidectomy
29
Q

What is the function of the parathyroid glands?

A
  • 4 small glands

* Produce PTH - regulates plasma Ca

30
Q

Name different causes of parathyroid hyperfunction

A

Primary:
• Often asymptomatic hypercalcaemia

Sporadic or familial (MEN-1)
• Adenoma
• Hyperplasia
• Carcinoma

Secondary:
Physiological response to decrease calcium renal failure

31
Q

What is the function of the hypothalamus?

A
  • Maintains homeostasis
  • Governs emotional behaviour
  • Links nervous system to endocrine system via pituitary gland
32
Q

Describe the anatomy and function of the pituitary gland?

A
  • Small gland, located in sella turcica
  • Connected to hypothalamus by pituitary stalk
  • Critical role in regulating other endocrine glands
33
Q

What is the function of the anterior pituitary?

A

Adenohypophysis
• Blood supply from hypothalamus
• Secretes ACTH, TSH, GH, PROLACTIN, FSH/LH
• Controlled by release factors from hypothalamus

34
Q

What is the function of the posterior pituitary?

A

Neurohypophysis
• Downgrowth of hypothalamus
• Secretes ADH, OXYTOCIN

35
Q

Describe the histology of the pituitary glands

A

Anterior pituitary - 3 major cell types:
• Pink ACIDOPHILS secrete GH and PRL
• Dark purple BASOPHILS secrete ACTH, TSH, FSH, LH
• Pale CHROMOPHOBES

36
Q

What is the most common cause of pituitary hyperfunction?

A

Pituitary adenoma

37
Q

Describe the histology of pituitary adenomas

A
  • Cells of same appearance as normal gland

* Classified by hormone(s) produced by the neoplastic cells - detected by immunohistochemical stains

38
Q

What are the effects of pituitary adenomas?

A

If functioning -> hormone excess

  • Prolactinoma -> galactorrhea, menstrual disorders
  • GH secreting -> acromegaly, gigantism
  • ATH secreting -> cushing’s disease
39
Q

What are the effects of large pituitary adenomas?

A 
Mass pressure effect:
• Radiograph abnormalities 
• Visual field abnormalities 
• Elevated intracranial pressure 
• Compression damage - hypopituitarism
40
Q

What are the different causes of pituitary hypofunction?

A
  • Compression by tumours - craniopharyngioma, metastatic
  • Trauma
  • Infection (rare) - TB, sarcoidosis
  • Post-partum ischaemic necrosis - Sheehan’s syndrome
41
Q

What types of hormones are released by the different layers of the adrenal cortex?

A
  • Zona glomerulosa - mineralocorticoids (aldosterone)
  • Zona fasciculata - glucocorticoids (cortisol)
  • Zona reticularis - sex steroids (oestrogen, androgens)
42
Q

What is the function of the adrenal medulla?

A

Neuroendocrine (chromaffin) cells
• Adrenaline/ noradrenaline in response to stress
• Maintain BP
• Extra adrenal paraganglia similar

43
Q

Describe the different adrenal pathologies

A
  • Hyperfunction
  • Hypofunction
  • Mass lesion - effect late
44
Q

What are three adrenal cortical hyperfunction syndromes?

A
  • Hypercortisolism– CUSHING’S SYNDROME
  • Hyperaldosteronism (Conn’s syndrome)
  • Adrenoginital syndormes
45
Q

What are the different causes of Cushing’s syndrome?

A

• Exogenous - iatrogenic steroids
• Endogenous
- ACTH dependent (pituitary adenoma -> cushing’s disease)
- ACTH independent (functioning adrenal adenoma)

46
Q

What is the difference between ACTH dependent and independent Cushing;s syndrome?

A

Cushing syndrome due to an ACTH-secreting pituitary adenoma is referred to as Cushing disease.

ACTH-independent disease (when the adrenal is making too much cortisol and the ACTH is therefore low)

47
Q

Describe hyperaldosteronism (Conn’s syndrome)

A
  • Bilateral idiopathic hyperplasia
  • Functioning adrenal adenoma
  • (Secondary hyperaldosteronism – physiological due to ↓renal perfusion ↑renin-angiotensin)
48
Q

Describe adrenogenital syndromes

A
  • Functioning adrenal tumour
  • Pituitary tumour - Cushings disease
  • Congenital adrenal hyperplasia – steroid enzyme deficiency
49
Q

What are acute causes of destruction of glands causing adrenal insufficiency?

A

Meningococcal septicaemia.

50
Q

What are chronic causes of destruction of glands causing adrenal insufficiency?

A 
Primary: Addison's disease 
• Autoimmune 
• Infections - TB
• Replacement
• Atrophy - prolonged steroid therapy 
• Congenital hypoplasia

Secondary: pituitary failure

51
Q

Describe adrenocortical adenoma

A
  • Functioning – hyperadrenal syndromes, atrophy of adjacent cortex
  • Non functioning – often incidental – imaging/autopsy
  • Yellow-brown circumscribed
52
Q

Describe adrenocortical carcinoma

A

Primary:
• More likely functional - virilising
• Most large > 20cm, haemorrhage and necrosis, cystic
• Metastasises by lymphatics and blood - invades adrenal vein

Metastatic carcinoma
• More common
• Lung, breast

53
Q

Describe histology of adrenocortical adenoma

A
  • Nuclei small
  • Some pleomorphism (“endocrine atypia”)
  • Cytoplasm eosinophilic to vacuolated, depends on lipid
  • Mitoses inconspicuous
54
Q

Name an adrenal medullary tumour

A

Pheochromocytoma

55
Q

Describe pheochromocytoma

A
  • Adrenal medulla neuroendocrine cells
  • Secrete catecholamines → hypertension
  • Usually benign behaviour, can be bilateral
56
Q

Describe histology of pheochromocytoma

A
  • Nests “Zellballen” of polygonal cells in vascular network

* Granular cytoplasm containing catecholamines

57
Q

Describe multiple endocrine neoplasias

A
  • Inherited disorders with underlying genetic mutation

* Hyperplasia/ neoplasms of endocrine organs – younger age, multifocal

58
Q

What are the distinct syndrome caused by multiple endocrine neoplasias?

A
  • MEN 1 (Wermer syndrome)

* MEN 2 (RET proto-ongogene mutations)

59
Q

Describe MEN 1 (wermer syndrome)

A

MEN 1 tumour suppressor gene mutation - defect in menin protein involved in regulating cell growth

  • Parathyroid hyperplasia and adenomas
  • Pancreatic and duodenal endocrine tumours (hypoglycaemia and ulcers)
  • Pituitary adenoma (prolactinoma)
60
Q

Describe MEN 2 (RET proto-ongogene mutations)

A
  • Medullary carcinoma of thyroid
  • Phaeochromocytoma
MEN 2A (Sipple syndrome): 
• Parathyroid hyperplasia

MEN 2B
• Neuromas of skin + mucous membrane, skeletal abnormalities
• Younger patients, aggressive

Endocrine System (29 decks)

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