Nuts and bolts of the endocrine system - part 2

Question 1

Endocrine glands

Answer 1

No duct system

Hormones are released at specific times in small amounts into the tissue fluids or blood vessels

Question 2

Endocrine definition

Answer 2

Action of the hormone on a target organ away from the secreting cell

Question 3

Autocrine definition

Answer 3

Action of the hormone on the secreting cell

Question 4

Paracrine definition

Answer 4

Action of the hormone on the adjacent cell

Question 5

Neuroendocrine definition

Answer 5

Neural stimulation of endocrine cells to secrete hormones

Question 6

Overall structure of endocrine glands

Answer 6

Functional unit consist of cuboidal secretory cells with a lumen at the centre

Secretory cells supported by myoepithelial cells

Question 7

Clinical manifestations of endocrine diseases

Answer 7

Hormone overproduction

Hormone underproduction

Tumour/ mass lesion which can be

• non-functional so has pressure effect
• associated with over production of hormones

Question 8

Pituitary gland divided into

Answer 8

Adenohypophysis/ anterior lobe

Neurohypophysis/ posterior lobe

Question 9

Cells of the anterior pituitary gland

Answer 9

Acidophils

Basophils

Chromophobe

Question 10

Acidophils

Answer 10

Take up acidic dyes

Question 11

Basophils

Answer 11

Take up basic dyes

Question 12

Chromophobe

Answer 12

No specific staining feature

Question 13

Somatotroph

Answer 13

Secretes growth hormone

Target organ: bones

Question 14

Lactotroph

Answer 14

Secretes prolactin

Target organ: breasts

Question 15

Corticotroph

Answer 15

Secretes adrenocorticotrophic hormone

Target organ: adrenal glands

Question 16

Gonadotroph

Answer 16

Secretes follicle stimulating hormone and luteinising hormone

Target organ: ovary and testis

Question 17

Thydrotroph

Answer 17

Secretes thyroid stimulating hormone

Target organ: thyroid gland

Question 18

Hormones from the posterior pituitary

Answer 18

Antidiuretic hormone
- facilitates absorption of water in kidneys

Oxytocin
- promotes contraction of smooth muscle in the uterus during childbirth and myoepithelial cells in the breast during breast feeding

Question 19

Pathology of the pituitary gland

Answer 19

Pituitary adenomas (benign tumours)

• arise from anterior lobe
• can be functional or non-functional
• constitute 10% of intra cranial neoplasms
• productive adenomas cause hyperpituitarism
• pressure effect causing hypopituitarism

Space occupying effect of functional or non-functional adenomas
- headaches, vomiting, nausea and diplopia, impaired vision

Question 20

Thyroid gland

Answer 20

Synthesises T4 (thyroxine) and T3 (triiodothyronine) which stimulates metabolic rate

Synthesis of T4 and T3 requires iodine

Lack of iodine leads to an enlarged thyroid gland termed goitre

Gland expands to absorb maximum concentration of iodine

Question 21

Normal thyroid gland

Answer 21

Weight = 35-45g

2 lobes and isthmus

Thyroid tissue is composed of follicles with variable sized lumina

Follicles contain colloid with eosinophilic or pink appearance

Question 22

Features of the thyroid gland

Answer 22

Very vascular

Endothelial cells lining the capillaries are fenestrated

Fenestration allows passage of hormones into the circulation

Para- follicular cells or clear (C) cells are found between the follicles

C cells secrete calcitonin which promotes reduction of calcium concentration in the blood

Question 23

Pathology of the thyroid gland

Answer 23

Goitre- euthyroid

Grave’s disease- hyperthyroid

Hashimoto’s disease- hypothyroid

Adenoma- euthyroid

Cancer- euthyroid

Question 24

Multi-nodular goitre

Answer 24

Lack of iodine leads to an enlarged thyroid gland

Due to hyperplasia and hypertrophy of thyroid cells

Gland enlarges to maximise amount of iodine absorbed

The increase in size overcomes the hormone deficiency and the patients are euthyroid

Question 25

Grave's disease

Answer 25

Auto-antibodies stimulate TSH receptors Diffuse enlargement of the thyroid due to hyperplasia of thyroid cells Infiltrative opthalmopathy Infiltrative dermopathy

Question 26

Infiltrative opthalmopathy

Answer 26

Accumulation of soft tissue and inflammatory cells behind the eye leading to proptosis

Question 27

Infiltrative dermopathy

Answer 27

Thickening and induration of the skin on the anterior shin Pre-tibial myxoedema

Question 28

Hashimoto's thyroiditis

Answer 28

Most common cause of hypothyroidism in areas where iodine is readily available An auto-immune disease- immune system destroys its own thyroid tissue Progressive depletion of thyroid cells by inflammation and replaced by fibrosis - decreased T3 and T4 - increased TSH

Question 29

Thyroid tumours

Answer 29

Follicular adenoma- benign tumour of the thyroid follicular cells Four main types of carcinoma - pappilary (75-85%): increased risk of lymph node metastasis - follicular (10-20%): increased mets to bone, lung and liver - medullary (5%): arise from C cells - anaplastic (<5%): older patients, poor prognosis

Question 30

Para-follicular cells

Answer 30

C cells secrete calcitonin which promotes reduction of calcium concentration in the blood Para- follicular cells (C cells) are found between the follicles C cells are the origin of medullary carcinoma of the thyroid

Question 31

Parathyroid glands

Answer 31

Secrete parathyroid hormone Controls the levels of calcium in the blood Decrease in blood calcium stimulates PTH secretion Chief cells with no lumen

Question 32

Pathology of parathyroid glands

Answer 32

Adenoma- involves one gland Hyperplasia- involves all four glands Both cause hypercalcaemia

Question 33

Adrenal glands

Answer 33

Paired glands Upper poles of the kidneys Consist of adrenal cortex and adrenal medulla which are embryologically, morphologically and functionally distinct

Question 34

Adrenal cortex derived from

Answer 34

The mesoderm

Question 35

Adrenal medulla derived from

Answer 35

The neural crest

Question 36

Normal adrenal gland

Answer 36

Characteristically orange/ yellow in colour because cells are rich in lipids

Question 37

Adrenal cortex

Answer 37

Divided into three distinct zones - zona glomerulose - zona fasciculata - zona reticularis Cells appear pale on histology becuase the lipids are cleared by chemicals during processing

Question 38

Functional zonation of the adrenal cortex (salt, sugar, sex)

Answer 38

Zona glomerulosa - minerlocorticoid - aldosterone - for absorption of sodium Zona fasciculata - glucocorticoids - cortisol and corticosterone - sex hormones Zona reticularis - 17 ketosteroids - sex hormones

Question 39

Pathology of the adrenal glands

Answer 39

Adrenocortical hyperactivity Adrenocortical insufficiency

Question 40

Adrenocortical hyperactivity

Answer 40

Due to hyperplasia, adenoma or cancer Cushing's syndrome (excess cortisol) Conn's syndrome (excess aldosterone) Adrenogenital syndrome (excess androgens)

Question 41

Adrenocortical insufficiency

Answer 41

Addision's disease

Question 42

Adrenal cortex adenoma

Answer 42

Non-functional cortical adenoma Incidental finding on abdominal imaging Functional adenomas can cause Cushing's or Conn's syndrome

Question 43

Adrenal medulla

Answer 43

Compact cells which secrete adrenaline and noradrenaline Fight or flight hormones Secretion results in vasoconstriction, increased heart rate, increased blood sugar levels

Question 44

Adrenal medulla cells

Answer 44

Neuroendocrine Darker staining than the adrenal cortex cells

Question 45

Phaechromocytoma

Answer 45

Tumour of the adrenal medulla 0.1-0.3% cause of treatable hypertension 10% tumour - familial as part of MEN2 - extra adrenal - bilateral - malignant - arise in childhood

Question 46

Cause of phaechromocytoma

Answer 46

Due to high levels of catecholamines

Question 47

Phaechromocytoma leads to

Answer 47

Precipitois increase BP and tachycardia Palpitations Headache Sweating Tremor Sense of apprehension