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Y3 Repro and Endo Pathology > Pathology of the Endocrine system 1 > Flashcards

Pathology of the Endocrine system 1 Flashcards

1
Q

What are hormones?

A

Chemical messengers secreted into the blood or extracellular fluid by one cell that affects the function of other cells

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2
Q

What are endocrine glands?

A

Collections of specialised cells that synthesise, store and release their secretions DIRECTLY into the blood stream

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3
Q

What are endocrine cells?

A

Cells with well developed RER (site of hormone assembling) and Golgi apparatus (site of hormone packaging into granules for intracellular storage and transport)

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4
Q

Steroid hormone-secreting cells contain?

A

Large cytoplasmic lipid bodies with hormone precursor molecules

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5
Q

Describe the 3 possible actions of hormones

A
  • Autocrine effect: cell secretes a hormone and it comes straight back onto a receptor on its own self
  • Paracrine effect: a cell secretes a hormone into the extracellular fluid in the tissue, impacting adjacent cells
  • Endocrine effect: hormone travels in the blood to a distant site to a target cell in a different organ
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6
Q

What are agonists?

A

Molecules that bind the receptor and induce all the post-receptor events that lead to a biologic effect (~ the “normal” hormone)

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7
Q

What are antagonists?

A

Molecules that bind the receptor and block binding of the agonist, but fail to trigger intracellular signalling events

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8
Q

Name the 4 hormonal chemical structure types, naming examples of each

A
  1. Peptides and proteins e.g. insulin, prolactin, ACTH, growth hormone, ADH, oxytocin
  2. Steroids e.g: glucocorticoids, mineralocorticoid, androgens, oestrogens, progestagens
  3. Amino acid derivatives e.g: catecholamines, thyroid hormones
  4. Fatty acid derivatives e.g. Prostaglandins, leukotrienes
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9
Q

Concentration of a hormone as seen by target cells is determined by which three factors?

A

1) Rate of production
2) Rate of delivery
3) Rate of degradation and elimination

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10
Q

What is negative feedback?

A

When output of a pathway inhibits inputs to the pathway

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11
Q

Describe the hypothalamic-pituitary axis as a negative feedback mechanism

A

1) Neurons in the hypothalamus secrete thyroid releasing hormone (TRH), which stimulates cells in the anterior pituitary to secrete thyroid-stimulating hormone (TSH).
2) TSH binds to receptors in the thyroid gland, stimulating synthesis and secretion of thyroid hormones, which affect probably all cells in the body
3) When blood concentrations of thyroid hormones increase to above a certain threshold, TRH-secreting neurons in the hypothalamus are inhibited and stop secreting TRH.

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12
Q

Describe the insulin/glucose feedback mechanism

A

1) Glucose from the ingested lactose or sucrose is absorbed in the intestine - level of glucose in blood rises
2) Elevation of blood glucose concentration stimulates endocrine cells in the pancreas to release insulin.
3) Insulin facilitates entry of glucose into many cells of the body -> blood glucose levels fall.
4) When the level of blood glucose falls sufficiently, the stimulus for insulin release disappears and insulin is no longer secreted

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13
Q

What are the main effects of hormones on target cells?

A
  1. Activation of enzymes and other dynamic molecules

2. Modulation of gene expression

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14
Q

Describe an endocrinopathy

A
  • A disease caused by the dysfunction of an endocrine gland
  • Increased activity (hyper…..) or decreased activity (hypo……) of the gland
  • Lesion affecting the gland itself, and also changes in distant sites of the body
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15
Q

Describe the effects of a primary hypofunction of the endocrine gland

A

Reduced hormone release due to:

  • Extensive destruction of secretory cells by disease process (eg. autoimmune attack)
  • Failure of endocrine gland to develop properly
  • Due to specific biochemical defect in synthetic pathway of a hormone
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16
Q

Describe the effects of a secondary hypofunction of the endocrine gland

A

Reduced hormone release due to a destructive lesion in one organ which interferes with the secretion of a trophic hormone (eg. pituitary gland) -> hypofunction of target endocrine gland

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17
Q

Describe the effects of a primary hyperfunction of the endocrine gland

A

Increased hormone release due to autonomous synthesis and secretion of hormone (mainly in neoplasms) at rate in excess of the body’s ability to use and degrade it

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18
Q

Describe the effects of a secondary hyperfunction of the endocrine gland

A

Increased hormone release due to increased secretion of a trophic hormone (eg. pituitary gland) -> long-term stimulation and hypersecretion of hormone by target endocrine gland

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19
Q

Describe hypersecretion of “hormones” by non-endocrine neoplasms

A

Some non-endocrine neoplasms secrete new humoral substances or hormones with characteristics of “native” hormones

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20
Q

Endocrine dysfunction due to failure of target cell response is due to?

A
  • Lack of adenylate cyclase in cell membrane

- Alteration in hormone receptors on cell surface

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21
Q

VITAMND of pathological mechanisms stands for?

A
  • Vascular
  • Inflammatory/infectious/immune
  • Traumatic, toxic
  • Anomalous
  • Metabolic
  • Neoplastic, nutritional
  • Degenerative
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22
Q

The pituitary gland sits ventral to?

A

The hypothalamus

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23
Q

The hypothalamus is involved in the production of which hormones?

A
  • ADH (vasopressin)
  • Oxytocin
  • Hypophyseotropic releasing hormones (RH) / inhibiting hormones (IH)
    e. g. Growth hormone, prolactin, thyrotropin
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24
Q

Acidophilic cells produce?

A
  • Growth hormone (STH; somatotropin)

- Prolactin (PRL): mammary gland, ovaries

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25
Q

Basophilic cells produce?

A
  • LH, FSH: gonads

- Thyroid stimulating hormone (TSH) -> thyroid gland Adenocorticotropic hormone (ACTH) -> adrenal cortex

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26
Q

Neurohypophysis is responsible for?

A

Nutritional and functional support of adenohypophysis (release of hypothalamic hormones into capillary bed of neurohypophysis)

27
Q

What are the major physiological effects and major target organs of growth hormone?

A
  • Promotes growth (indirectly), control of protein, lipid and carbohydrate metabolism
  • Liver, adipose tissue
28
Q

What are the major physiological effects and major target organs of Adrenocorticotropic hormone?

A
  • Stimulates secretion of glucocorticoids

- Adrenal gland (cortex)

29
Q

What are the major physiological effects and major target organs of Prolactin

A
  • Milk production

- Mammary gland

30
Q

What are the major physiological effects and major target organs of Antidiuretic hormone?

A
  • Conservation of body water

- Kidneys

31
Q

What are the major physiological effects and major target organs of oxytocin

A

Stimulates milk ejection and uterine contractions

- ovary and testis

32
Q

Describe diabetes insipidus

A
  • Reduced ADH (vasopressin) effect

- Clinical signs: polyuria, polydipsia

33
Q

Describe central diabetes insipidus

A

dog, cat, horse, rat

Impaired hypothalamic production, transport, storage and/or release from neurohypophysis

34
Q

Describe nephrogenic diabetes insipidus

A
  • Kidney cannot concentrate the urine despite normal vasopressin production
  • Due to congenital V2 receptor defect (hereditary in Husky) or congenital or acquired renal changes
35
Q

Name some congenital defects of the pituitary gland and hypothalamus

A
  • Hypoplasia, aplasia (calves: with cyclopia, arhinencephaly)
  • Pituitary cysts (Rathke’s cysts): can grow towards larynx and cause dyspnoea
  • Juvenile panhypopituitarism: “pituitary dwarfism” (dog, autosomal recessive)
  • Giantism / acromegaly: excessive GH production
36
Q

Describe some regressive changes and inflammation of the pituitary gland and hypothalamus

A
  • atrophy (with age; horse, dog)

- pituitary inflammation: rare -> abscess formation

37
Q

Describe some regenerative processes of the pituitary gland and hypothalamus

A
  • Nodular hyperplasia (old horses, dogs, laboratory rats) = Excessive regenerative attempt
  • Adenomas of adenohypophysis (old horses, dogs, laboratory rats)
38
Q

Adenomas of adenohypophysis are associated with?

A
  • hormonal hypersecretion
  • compression of adjacent structures
    → hypopituitarism, Diabetes insipidus, CNS symptoms
39
Q

ACTH producing adenomas are associated with … in dogs

A

Cushings syndrome

40
Q

ACTH producing adenomas are associated with … in horses

A

Cushing syndrome and/or symptoms due to compression of adjacent structures e.g. hypothalamus

41
Q

Cushings disease is also known as?

A

Hyperadrenocorticism

42
Q

Describe the features of Cushings disease

A
  • Bilaterally symmetrical hyperplasia of adrenal cortices
  • Characterised by elevated glucocorticoid levels (dogs!, cats, horses)
  • Clinical signs dependant on excess hormonal activity
43
Q

Cushings disease has what associated signs?

A
  • Polydipsia, polyuria, polyphagia
  • Obesity (trunk), atrophy of skeletal muscle
  • Alopecia, epidermal atrophy, osteopenia
  • Secondary diabetes mellitus
44
Q

What does PPID stand for?

A

pituitary pars intermedia dysfunction

45
Q

Describe cushings disease in horses

A

In older horses with ACTH-producing tumours of adenohypophysis (pars intermedia)

46
Q

Clinical signs of Equine cushings occur due to?

A

a) expansile growth of tumour

b) ACTH production (endocrine activity of tumour)

47
Q

What are the effects of expansive tumour growth?

A

Compression of neurohypophysis and hypothalamus and impairment of hypothalamic centres ability to regulate cyclic hair growth, appetite and body temperature

48
Q

ACTH production has what effects in equine cushings?

A
  • Polydipsia/polyuria, polyphagia, insulin-resistant hyperglycaemia, glucosuria
  • Increased susceptibility to infectious diseases (immuno-suppression)
49
Q

Describe the feedback mechanism of the hypothalamus

A

Thyrotropin-RH [TRH]

→ adenohypophysis: TSH → thyroid gland: T3, T4

50
Q

Name the cells of the thyroid gland

A

1) thyroid follicular epithelial cells [colloid = proteinaceous depot of thyroid hormone precursor]
2) parafollicular or C cells (nestled in spaces between thyroid follicles): secrete calcitonin

51
Q

Name the two principle thyroid hormones

A

1) thyroxine (known as T4)

2) triiodothyronine (T3)

52
Q

What are the effects of thyroid hormones?

A

Metabolism: increase in basal metabolic rate; increased oxidative phosphorylation
Lipid metabolism: stimulation of fat mobilisation (fatty acids in plasma↑)
Carbohydrate metabolism: stimulation of carbohydrate metabolism

53
Q

Which animals are affected by primary hypothyroidism?

A

Older dogs

54
Q

What are the causes of primary hypothyroidism?

A
  • Loss of functional parenchyma [aplasia, hypoplasia, atrophy, inflammation, tumours, irradiation]
  • Deficiency of hormone components (esp. iodine)
  • Chemical blockage of hormone production
  • Resection of gland
55
Q

What are the consequences of primary hypothyroidism?

A
  • increased body weight
  • dermatological
  • reproductive
  • goitre
  • myxoedema
56
Q

Define Goitre

A

Enlarged thyroid gland due to iodine deficiency

57
Q

What are the dermatological effects of hypothyroidism?

A

Thin coat, bilateral alopecia, hyperkeratosis, hyperpigmentation

58
Q

What are the reproductive effects of hypothyroidism?

A

Reduced libido, abnormal oestrous cycles, low sperm counts

59
Q

What is myxoedema?

A

Mucoid oedema in (sub)cutis and mucosa, mainly in fetal/neonatal hypothyroidism [pigs, sheep, goats]

60
Q

Which animals mostly get hyperthyroidism?

A

older cats

61
Q

What are the consequences of hyperthyroidism?

A

due to increased basic metabolism

  • Weight loss
  • Hepatic lipidosis and necrosis due to glycogen deficiency
  • Heart: left ventricular hypertrophy
  • Leads to atrophy of normal parenchyma because of inhibition of TRH and TSH secretion (negative feedback)
62
Q

Describe the epithelial tumours of thyroid glands

A
  • Most frequent in dogs and cats, moderately so in horses, rare in others
  • Predominantly in areas of endemic goitre
  • Adenomas: hyperthyroid (toxic) adenomas: produce hormone (cats!)
  • Carcinoma: early haematogenous metastasis into lung; follicular, papillary or solid growth
63
Q

Name the mesenchymal tumours of thyroid glands

A

Haemangiomas, fibromas, osteochondromas, (fibro)sarcomas

Y3 Repro and Endo Pathology (5 decks)

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