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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
Describe differentiated thyroid carcinoma - follicular carcinoma
* Rare, usually solitary * Malignant cells breach capsule * Metastases - blood, bones • RAS mutation or translocation
26
Describe differentiated thyroid carcinoma - papillary carcinoma
* Usually < 50yrs * BRAF mutation or RET/PTC gene rearrangement * Associated with exposure to ionising radiation * Spreads via lymphatics * Excellent prognosis (95% survival)
27
Describe the histology of DTC - papillary carcinoma
* Papillary projections * Empty nuclei * Psammoma bodies * May be cystic
28
Describe thyroid medullary carcinoma
* Malignant tumour of C cells * Produces calcitonin (+/- other polypeptides) * 70% sporadic * Prophylactic thyroidectomy
29
What is the function of the parathyroid glands?
* 4 small glands | * Produce PTH - regulates plasma Ca
30
Name different causes of parathyroid hyperfunction
Primary: • Often asymptomatic hypercalcaemia Sporadic or familial (MEN-1) • Adenoma • Hyperplasia • Carcinoma Secondary: Physiological response to decrease calcium renal failure
31
What is the function of the hypothalamus?
* Maintains homeostasis * Governs emotional behaviour * Links nervous system to endocrine system via pituitary gland
32
Describe the anatomy and function of the pituitary gland?
* Small gland, located in sella turcica * Connected to hypothalamus by pituitary stalk * Critical role in regulating other endocrine glands
33
What is the function of the anterior pituitary?
Adenohypophysis • Blood supply from hypothalamus • Secretes ACTH, TSH, GH, PROLACTIN, FSH/LH • Controlled by release factors from hypothalamus
34
What is the function of the posterior pituitary?
Neurohypophysis • Downgrowth of hypothalamus • Secretes ADH, OXYTOCIN
35
Describe the histology of the pituitary glands
Anterior pituitary - 3 major cell types: • Pink ACIDOPHILS secrete GH and PRL • Dark purple BASOPHILS secrete ACTH, TSH, FSH, LH • Pale CHROMOPHOBES
36
What is the most common cause of pituitary hyperfunction?
Pituitary adenoma
37
Describe the histology of pituitary adenomas
* Cells of same appearance as normal gland | * Classified by hormone(s) produced by the neoplastic cells - detected by immunohistochemical stains
38
What are the effects of pituitary adenomas?
If functioning -> hormone excess * Prolactinoma -> galactorrhea, menstrual disorders * GH secreting -> acromegaly, gigantism * ATH secreting -> cushing's disease
39
What are the effects of large pituitary adenomas?
``` Mass pressure effect: • Radiograph abnormalities • Visual field abnormalities • Elevated intracranial pressure • Compression damage - hypopituitarism ```
40
What are the different causes of pituitary hypofunction?
* Compression by tumours - craniopharyngioma, metastatic * Trauma * Infection (rare) - TB, sarcoidosis * Post-partum ischaemic necrosis - Sheehan's syndrome
41
What types of hormones are released by the different layers of the adrenal cortex?
* Zona glomerulosa - mineralocorticoids (aldosterone) * Zona fasciculata - glucocorticoids (cortisol) * Zona reticularis - sex steroids (oestrogen, androgens)
42
What is the function of the adrenal medulla?
Neuroendocrine (chromaffin) cells • Adrenaline/ noradrenaline in response to stress • Maintain BP • Extra adrenal paraganglia similar
43
Describe the different adrenal pathologies
* Hyperfunction * Hypofunction * Mass lesion - effect late
44
What are three adrenal cortical hyperfunction syndromes?
* Hypercortisolism– CUSHING’S SYNDROME * Hyperaldosteronism (Conn’s syndrome) * Adrenoginital syndormes
45
What are the different causes of Cushing's syndrome?
• Exogenous - iatrogenic steroids • Endogenous - ACTH dependent (pituitary adenoma -> cushing's disease) - ACTH independent (functioning adrenal adenoma)
46
What is the difference between ACTH dependent and independent Cushing;s syndrome?
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
Describe hyperaldosteronism (Conn's syndrome)
* Bilateral idiopathic hyperplasia * Functioning adrenal adenoma * (Secondary hyperaldosteronism – physiological due to ↓renal perfusion ↑renin-angiotensin)
48
Describe adrenogenital syndromes
* Functioning adrenal tumour * Pituitary tumour - Cushings disease * Congenital adrenal hyperplasia – steroid enzyme deficiency
49
What are acute causes of destruction of glands causing adrenal insufficiency?
Meningococcal septicaemia.
50
What are chronic causes of destruction of glands causing adrenal insufficiency?
``` Primary: Addison's disease • Autoimmune • Infections - TB • Replacement • Atrophy - prolonged steroid therapy • Congenital hypoplasia ``` Secondary: pituitary failure
51
Describe adrenocortical adenoma
* Functioning – hyperadrenal syndromes, atrophy of adjacent cortex * Non functioning – often incidental – imaging/autopsy * Yellow-brown circumscribed
52
Describe adrenocortical carcinoma
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
Describe histology of adrenocortical adenoma
* Nuclei small * Some pleomorphism (“endocrine atypia”) * Cytoplasm eosinophilic to vacuolated, depends on lipid * Mitoses inconspicuous
54
Name an adrenal medullary tumour
Pheochromocytoma
55
Describe pheochromocytoma
* Adrenal medulla neuroendocrine cells * Secrete catecholamines → hypertension * Usually benign behaviour, can be bilateral
56
Describe histology of pheochromocytoma
* Nests “Zellballen” of polygonal cells in vascular network | * Granular cytoplasm containing catecholamines
57
Describe multiple endocrine neoplasias
* Inherited disorders with underlying genetic mutation | * Hyperplasia/ neoplasms of endocrine organs – younger age, multifocal
58
What are the distinct syndrome caused by multiple endocrine neoplasias?
* MEN 1 (Wermer syndrome) | * MEN 2 (RET proto-ongogene mutations)
59
Describe MEN 1 (wermer syndrome)
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
Describe MEN 2 (RET proto-ongogene mutations)
* 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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