Chapter 10 - Endocrine/metabolic Flashcards
Which is the major, metabolically active thyroid hormone?
T3
Name three things that inhibit TSH secretion
Stress Steroids Dopamine Thyroid hormones Somatostatin
Thyrotropin-releasing hormone stimulates release of TSH and which other hormone?
Prolactin
Which keratinocyte genes are stimulated by T3?
Wound-healing
Myxoedema is due to increased deposition of what?
Mucin
Why do hypothyroid dogs have increased triglyceride levels?
Decreased plasma clearance
What % of euthyroid dogs can have a one-off low T4?
20%
What % of hypothyroid dogs have antithyroglobulin antibodies?
50%
Antithyroglobulin antibodies are more common in which dog breeds?
Great Danes, Borzois, Irish Setters, Old English sheepdogs and Dobermans
Can you see antithyroglobulin antibodies in euthyroid dogs with other endocrine diseases?
Yes
In which zone of the adrenal gland are glucocorticoids produced?
Zona fasciculata
Why do glucocorticoids cause thinning and fragility of the dermis?
They inhibit fibroblast proliferation, collagen and ground substance proliferation
What % of dogs have pituitary dependent hyperadrenocorticism?
80-85%
Which anatomical sites are most commonly affected by calcinosis cutis?
Dorsal neck, rump, axillae and groin
What % of cats have pituitary dependent hyperadrenocorticism?
~80%
Where is growth hormone (somatotropin) produced?
Adenohypophysis (anterior pituitary)
What regulates growth hormone secretion?
GHRH (growth hormone releasing hormone) and somatostatin (produced by hypothalamus)
What impairs insulin-like growth factor-1?
Steroids and oestrogens
Name the anatomical sites most obviously affected by myxoedema with acromegaly
Face and extremities
Do you get hyper- or hypotrichosis with increased growth hormone secretion?
Hypertrichosis
In GSDs, is pituitary dwarfism an autosomal recessive or dominant trait?
Autosomal recessive
Which hormones are deficient in GSDs with pituitary dwarfism?
Growth hormone, TSH, prolactin, gonadotropins
At what age to clinical signs become apparent in GSDs with pituitary dwarfism?
2-3 months
Which zone of the adrenal gland produces androgens and progesterone?
Zona reticularis
Which clinical sign is highly suggestive of hyperoestrogenism in male dogs?
Linear preputial erythema
In which breeds has Alopecia X been reported?
Pomeranians Alaskan Malamutes Chows Keeshonds Min/toy poodles Samoyeds Schipperkes
What are the initial signs of Alopecia X?
Dull, dry coat and loss of primary hairs
Which anatomical sites are spared in Alopecia X?
Head and extremities
Name three cutaneous clinical signs that can be seen with diabetes mellitus in dogs and cats
Bacterial pyoderma
Seborrhoea
Thin and hypotonic skin
Alopecia
What are the differentials for necrolytic migratory erythema/SND?
PF
SLE
Zinc deficiency/responsive dermatosis
Generic dog food dermatosis
What make up the ‘red, white and blue’ layers on histopathology of necrolytic migratory erythema/SND
Red = diffuse parakeratosis White = vacuolaton of keratinocytes and oedema Blue = basal cells hyperplasia superficial interstitial to lichenoid infiltrate
What are the histopathological findings of the skin of dogs with hyperadrenocorticism?
- Thin epidermal and follicular epithelium, which can be 1-3 nucleated cell layers thick.
- If calcinosis cutis is present, the epidermis is frequently hyperplastic and can be ulcerated.
- Orthokeratotic hyperkeratosis; marked follicular keratosis, sometimes with comedone formation.
- Thin dermis.
- Hair follicles that are frequently in telogen or kenogen.
- Sebaceous gland atrophy and/or sebaceous melanosis.
- Dysplastic follicles
- Variable hyperpigmentation.
Mineralization of the external root sheath can be seen in normal old dogs and dogs of which breed?
Poodles
Which treatments have reportedly been effective at reducing/resolving calcinosis cutis in dogs?
DMSO (Tolon et al. 2018)
Minocycline (Jang et al. 2013, Cho et al. 2017)
Tetracycline (Harvima et al. 2020)
Can the hepatopathy, hypoaminoacidemia, and aminoaciduria associated with hepatocutaneous syndrome be seen without NME/SND signs?
Yes - they may appear after diagnosis.
The presence or absence of skin lesions at time of diagnosis does not appear to affect survival (Loftus et al. 2022)
In the study by Loftus et al. (2022), which treatments for HCS were associated with increased survival?
At least two IV amino acid infusions
A home cooked, high protein diet
Supplements targeting depleted AAs essential for collagen synthesis (lysine, proline), supporting the urea cycle (arginine and ornithine), and for glutathione synthesis(cysteine, glycine, and SAMe) are recommended but were not found to significantly affect survival.
Plasma levels of which amino acids are low in dogs with HCS?
Alanine, glutamine, glycine, lysine, proline, threonine, 1-methylhistidine and cystathionine
What is the commonly reported signalment for HCS/SND?
Older, male, small breed dogs e.g. cocker spaniel, Shetland sheepdog, Shih Tzu, and West Highland white terrier
An excess of which amino acid in urine can help to diagnosis HCS?
Lysine and methionine
How does trilostaine treat HAC?
The drug is a competitive inhibitor of the 3β-hydroxysteroiddehydrogenase / isomerase system required to synthesise cortisol, aldosterone, and androstenedione.
Which breeds are more commonly affected by HAC?
Miniature poodle, dachshund, Irish setter, bassett hound, miniature schnauzer and toy poodle (Hoffman et al. 2018) Bichon frise (O'Neill et al. 2016)
Which breeds are least likely to develop HAC?
Dobermann pinscher, rottweiler, collie and great Dane
(Hoffman et al. 2018)
Border collie and Labrador (O’Neill et al. 2016)
In healthy individuals, corticotropin-releasing hormone (CRH), produced by the _________, is the principal simulant of episodic secretion of adrenocorticotropic hormone (ACTH) by the pars ____ which stimulates glucocorticoid production and secretion from the adrenal glands
Hypothalamus
Distalis
True or false; In addition to the pars distalis, ACTH is also produced by the B cells of the pars intermedia where its secretion is regulated by tonic dopaminergic inhibition
True
Have bilateral adrenal tumours been reported in dogs with HAC?
Yes, uncommonly
Which hormone, other than cortisol, can be secreted by adrenal tumours?
17-OH-progesterone
What are the most common non-cutaneous clinical signs of HAC in dogs?
- PU/PD 82–91%
- PP 46–57%
- Abdominal enlargement 67–73%
- Hepatomegaly 50–67%
- Systemic hypertension 31–86%
What are the common biochemical changes in dogs with HAC?
- Increased ALP 76–100% and ALT 80–95%
- Hypercholesterolaemia 73–90%
- Decreased urea concentration 34–56%
- Hyperglycaemia 20–57%