Flashcards
Endocrine system pathology 2
Flashcards do conjunto (59)
- 1What are the thyroid hormones?Thyroxin (T4) and Triiodothyronine (T3)
- 2What is the normal hypothalamic-pituitary-thyroid axis?- Hypothalamus produces TRH
- Pituitary gland produces TSH
- Acts on the thyroids and follicular cells
- T3 and T4 produced
- Negative feedback on hypothalamus and pituitary - 3What happens in primary hyperthyroidism?- Autonomous thyroid hormone production by bilateral or unilateral multinodular hyperplasia and/or follicular neoplasia (adenoma or carcinoma)
- Increase in T3 and T4
- Increased negative feedback on hypothalamus and pituitary
- Decreased TRH and TSH (no effect on autonomous thyroid hormone production) - 4Give features of feline hyperthyroidism.• Relatively common condition in middle-aged and older cats
• Usually caused by multinodular hyperplasia (“adenomatous hyperplasia”) and/or follicular adenoma(s)
• Bilateral thyroid involvement in >70% of cases
• Thyroid carcinomas are uncommon in cats (<2% of cases) - 5What happens in feline hyperthyroidism typically related to the metabolic effects of thyroid hormones?• Increased metabolic rate
• Interaction with CNS causing increased
sympathetic drive - 6What are the clinical features of feline hyperthyroidism?• Palpable goitre –unilateral or bilateral
• Weight loss
• Polyphagia
• Hyperactivity
• Tachycardia
• Heart murmur
• Intermittent GI signs (V/D) - 7What are features of thyroid neoplasia in dogs?• Most canine thyroid tumours are non-functional
• In dogs, thyroid follicular carcinomas are more common than adenomas, and can be bilateral
• Hyperthyroidism occurs in 10-20% of thyroid carcinomas
• Thyroid carcinomas may invade local structures e.g. trachea, larynx, neck muscles, oesophagus, nerves/blood vessels and metastatic spread to lungs (via invasion of thyroid veins) often occurs before local lymph node metastases - 8What can happen uncommonly in thyroid neoplasia in dogs?May arise from ectopic thyroid tissue in the mediastinum (“heart-base tumour” differential) or the base of the tongue
- 9What are the causes of hyperthyroidism?1. Excess production of T3 and T4
Primary: Functional (T4-/T3-secreting) thyroid follicular cell hyperplasia, adenomas or carcinomas - 10What is the main species affected by hyperthyroidism?Cats
- Less commonly dogs - 11What happens in primary hypothyroidism?- Hypothalamus produces TRH
- Pituitary gland produced TSH
- Most commonly due to loss of thyroid follicular cells (primary hypofunction)
- Reduced levels of T3 and T4 - 12What are the main mechanisms of primary hypothyroidism in dogs?1. Lymphocytic thyroiditis
2. Idiopathic follicular atrophy
- Iatrogenic
- Neoplastic disease
- Congenital hypothyroidism (primary and secondary) - 13What is lymphocytic thyroiditis?• Autoantibodies against thyroid follicular cell antigens e.g. thyroglobulin
• Lymphocytic infiltration and destruction of follicles by cytotoxic T-cells
- Fibrosis and residual small, widely separated follicles - 14What is idiopathic follicular atrophy?• Primary degeneration of follicles with minimal inflammation and replacement by adipose tissue
- 15What are iatrogenic mechanisms of hypothyroidism?Removal or destruction of the thyroid glands following treatment for hyperthyroidism e.g. bilateral thyroidectomy, radiation therapy or anti-thyroid drugs
- 16What are congenital hypothyroidism mechanisms?(affects bone growth causing dwarfism)
Primary: Abnormal development of the thyroid glands (e.g. thyroid hypoplasia or aplasia) or inability to generate thyroid hormones
Secondary: Congenital pituitary abnormality affecting TSH production - 17What are the clinical features in hypothyroidism?1. Metabolic: Reduced metabolic rate: Lethargy, weight gain, exercise intolerance
2. Dermatological:
• Bilaterally symmetrical alopecia (persistence of telogen phase)
• Myxoedema - non-pitting thickening of skin (mucopolysaccharide and hyaluronic acid accumulation)
• Secondary infections e.g. bacteria, Malassezia
3. Cardiovascular: Bradycardia, arrhythmias
4. Neuromuscular disease, infertility in bitches - 18What are the causes of hypothyroidism?Insufficient production of T3 and T4
Primary: Destruction and loss of thyroid tissue - 19What is the main species affected with hypothyroidism?Dog
- 20What hormone is produced in the parathyroid?Parathyroid hormone (PTH)
- 21What are the mechanisms of hyperparathyroidism?1. Primary hyperparathyroidism
2. *Parathyroid hormone-related protein production by neoplasms*
• Referred to as Humoral hypercalcaemia of malignancy or pseudohyperparathyroidism
3. *Hyperparathyroidism secondary to chronic kidney disease*
4. Hyperparathyroidism secondary to nutritional imbalances - 22What is the normal biological action of PTH?- Decreased blood Ca causes increased PTH secretion
- Increased blood Ca causes reduction in PTH secretion - 23What does PTH act on?1. KIDNEY
- Increases calcium reabsorption and decreases phosphorus reabsorption.
- Activation of calcitriol synthesis ( 1, 25-OH Vitamin D)
2. BONE
- Bone resorption by osteoclasts - mobilization of calcium
3. GI TRACT
- Promotes absorption of calcium - 24What is the anatomy of the parathyroid?- in each thyroid gland - one internal and one external
4 in total - 25What happens in primary hyperparathyrodism?- Chief cell adenoma or focal/multifocal nodular hyperplasia, or chief cell carcinoma (rare)
- Increase in PTH
- Blood calcium increase (hypercalcaemia)
- Reduced PTH secretion from normal chief cells
- Atrophy of remaining parathyroid glands - 26What happens in Humoral hypercalcaemia of malignancy (pseudohyperparathyroidism)?- Some non-parathyroid tumours produce parathyroid hormone-related protein
- Anal sac apocrine gland adenocarcinoma (dogs)/ lymphoma/ some carcinomas/ multiple myeloma
- Produce PTHrP
- Binds to tissue PTH receptors (bone and kidney)
- Hypercalcaemia
- Persistent hypercalcaemia will cause atrophy of parathyroid glands - 27What are the manifestation of primary hyperparathyroidism and humoral hypercalcaemia of malignancy?1. Effects of hypercalcaemia
• Anorexia, vomiting, constipation (decreased GI smooth muscle contraction)
• Generalised muscular weakness (decreased neuromuscular excitability)
• Polyuria/Polydipsia (impaired renal concentrating ability and toxic effects on renal tubules)
• Soft tissue mineralisation
2. Increased bone resorption
• Fibrous osteodystrophy (may be mild) - 28What happens with renal secondary hyperparathyroidism?- Chronic kidney disease
- Reduced GFR, retention of phosphate (hyperphosphataemia)
- Reduced cacitriol synthesis by renal tubules
- Decreased regulatory effect of calcitriol on PTH synthesis
- Increased TPH
- Renal osteodystrophy
- Phosphorus also decreases blood calcium so increasing PTH - 29What happens in nutritional secondary hyperparathyroidism?- Dietary calcium:phosphate imbalance
Low calcium
High phosphorus with normal or low calcium
Vitamin D deficiency
- Blood calcium decreased
- Increased PTH
- Fibrous osteodystrophy - 30Why would an animal have nutritional hyperparathyroidism?Dogs & cats fed largely/entirely on meat or
offal (excess phosphorus:low calcium )
Horse on grain or grain byproducts
e.g. bran (excess phosphorus) - 31What are the causes for hyperparathyroidism?Excess parathyroid hormone production
• Primary: Function tumour or nodular hyperplasia
• Secondary: Chronic renal disease or Nutritional imbalance Parathyroid hormone-related peptide production
• Some neoplastic diseases - 32What are the main species affected with hyperparathyroidism?Dog > cat
less common in horse - 33What is a condition of the pituitary and the hypothalamus?Pituitary pars intermedia dysfunction (PPID)
- 34What are features of the equine pituitary?1. Infundibular stalk
2. Pars distalis
3. Pard intermedia (melanotropes)
4. Pars nervosa Neurohypophysis - 35What makes the adenohypophysis?- Pars distalis
- Pars intermedia - 36What happens with the melanotropes in the equine pituitary?- Pars intermedia
- Periventricular nucleus
- Dopaminergic neurons - 37What are features of the pars intermedia function?• Melanotropes produce pro-opiomelanocortin (POMC) and convert it into a wide range of hormones e.g. MSH, β-endorphin
• This activity is inhibited by dopamine released from the periventricular neurones that synapse to the melanotropes - 38What happens in PPID?• Age-related neuronal degeneration with loss of dopaminergic inhibitory input to the melanotropes
• Results in melanotrope hyperplasia & adenoma formation and increased production of POMC-derived hormones - 39What can happen with pituitary adenomas?- Can compress other parts of the pituitary
- Occasionally, large pituitary tumours
can compress the overlying hypothalamus or the optic chiasm - 40What are the clinical manifestations of PPID?• Hirsutism (fail to shed hair)
• Hyperhidrosis (sweating)
• Muscle weakness
• Increased appetite
• PU/PD
• Lethargy/docile
• Laminitis - 41What are the mechanisms for PPID?Mechanisms poorly understood but may reflect compressive and destructive effects of large tumours on the pituitary and hypothalamus
- 42What is the cause of PPID?Increased production of POMC-derived hormones
• Secondary melanotrope hyperplasia and adenoma formation following decreased dopaminergic inhibition - 43What is the main species affected by PPID?Horse
- 44What are features of acromegaly?- Generally rare/uncommon …. except in cats
- Caused by a growth hormone (GH)-secreting (somatotroph) pituitary tumour (usually a slow growing adenoma)
- Feline acromegaly has recently been recognised as being quite common in diabetic cats (~25% of diabetic cats had concurrent acromegaly) - 45What is the main clinical signs with acromegaly?May develop broad facial features
- 46What is diabetes insipidus?Insufficient ADH production/release from the hypothalamus/pituitary
or
Renal tubules insensitive to ADH - 47what does diabetes insipidus cause?PU/PD due to inability of kidneys to concentrate urine
- 48What is the cause of central diabetes insipidus (CDI)?Include injury/destruction of the hypothalamus or pituitary
- 49Give uncommon causes of central diabetes insipidus.• Trauma
• Neoplastic disease e.g. pituitary tumour
• Inflammatory/infectious disease - 50What causes nephrogenic diabetes insipidus (NDI)?Renal tubules being insensitive to ADH
- 51Give features of NDI.1. Primary NDI very rare congenital disease e.g. mutation affecting the ADH receptor
2. Secondary (acquired) NDI can be associated with various metabolic, endocrine and renal diseases
• Pyelonephritis, renal failure
• Hyperadrenocorticism
• Hypercalcaemia
• Hypokalaemia
• Pyometra - 52What hormone(s) are increased in hyperthyroidism?Thyroxine and Triiodothyronine (T4 and T3)
- 53What is the most common cause of feline hyperthyroidism?Primary hyperthyroidism due to thyroid multinodular hyperplasia (“adenomatous hyperplasia”) and/or follicular adenoma(s). Often bilateral involvement.
- 54What is the most common type of thyroid tumour in the dog?Thyroid follicular carcinoma
- 55What is the most common cause of hypothyroidism in dogs?Primary hypothyroidism due to lymphocytic thyroiditis or idiopathic follicular atrophy
- 56What change in blood calcium levels may occur as a result of parathyroid hormone-related peptide production by tumours?Hypercalcaemia (high Ca)
- 57What is the most common cause of secondary hyperparathyroidism?Chronic kidney disease
- 58In PPID, what primary event is thought to precede the development of pituitary melanotrope hyperplasia or adenoma formation?Degeneration of dopaminergic neurons that normally inhibit melanotrope hormone production
- 59What is the cause of acromegaly in cats?Primary hyperfunction due to a growth-hormone secreting pituitary tumour. Adenoma most common
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- 4. Endocrine (Endocrine system pathology - Ross Harley) FlashCards sobre Endocrine system pathology 2, criado por Rachael Jones em 22-11-2018.
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