Pituitary Endocrinopathies Flashcards
What clinical problems occur due to pituitary disorders?
Neuro signs - seizures, behavioural changes
Alterations in BW, size and growth
Altered cycling, libido and fertility
PU/PD
If an animal is truly polydipsic and polyuric, what are the only two explanations?
- Primary polydipsia
- Renal dysfunction
- Unable to concentrate urine volume normally
What could renal dysfunction causing PUPD be due to?
Reduced nephron number
Enough nephrons, not functioning
Osmotic diuresis
ADH insensitivity/lack of ADH
What are the intracranial effects seen with pituitary disorders?
Various non-specific neuro signs
Rarely seizures
Depression, under-response to external stimuli
Pituitary central so neuro changes usually bilateral
What are the altered endocrine functions seen with pituitary disorders?
Hypersomatotrophism
Hyposomatotrophism
Diabeters insipidus
PD-hyperAC
Outline the pathogenesis of hypersomatotrophism…
- Autonomous GH production
- Results in increased IGF1 (insulin-like growth factor 1)
- Increased IGF1 produces:
- Tissue proliferation
- Insulin resistance
Outline the pathogenesis of hypersomatotropism in dogs…
GH producing mammary tissue
Due to chronic inappropriate production/exposure to progesterone
Outline the pathogenesis of hypersomatotrophism in cats…
GH producing pituitary tumour
What is the history and clinical signs seen in dogs with hypersomatotrophism…
Intact females Males with history of progestin administration Thick set facial features Increased interdental space Insulin resistance \+/- PUPD If DM, difficult to control
Describe the link between GH and IGF1
GH acts on liver
Need insulin in system to work on liver
Liver produces IGF1
Why is IGF1 more useful to measure than GH? What is necessary to produce IGF1?
GH pulsatile so peaks and troughs
IGF1 not so variable
Need insulin to produce IGF1
Why may you have no IFG1 detectable in a newly diagnosed DM cat?
No insulin
Give insulin supplement and measure again
What is fructosamine?
Compound that forms when glucose binds irreversible to albumin. Rate that occurs is dependant on glucose and albumin conc. So is a good biomarker for blood glucose for the last 3 weeks.
Describe the clinical signs of feline hypersomatotropism…
PUPD
Increased appetite
Overshot mandible, increased body size, organomegaly
Insulin resistance
Clinically significant glucose intolerance
Poorly controlled DM
Describe the management of acromegaly in cats…
Aggressive insulin treatment Radiotherapy Hypophysectomy Pasireotide injections (Multi-receptor somatotroph antagonist)
Describe hypophysectomy for feline hypersomatotrophism…
Highly successful in certain circumstances
Almost instantaneous normalisation of IGF1
Given twice daily insulin
85% of cats off insulin within a month
What should you do if you suspect hypersomatotrophism in a cat?
Index of suspicion based on serum IGF1
Confirmation based on MRI/CT
Sample all diabetics at early checkup
Describe the control of body water with vassopressin (ADH)
- V1, V2, V3 receptors
- V2 activates cytoplasmic aquaporin-2
- Aquaporin moves to tubular luminal membrane
- Allows tubular water resporption
- Water moves extracellulary down conc gradient
- Endothelial cell V2 receptors
What is central diabetes insipidus?
Absolute vasopressin deficiency
Primary pituitary problem
What is nephrogenic or renal diabetes insipidus?
Vasopressin resistance
Primary renal problem or metabolic problem causing renal dysfunction
What is the history and clinical signs of a central diabetes insipidus?
Marked PUPD usually >200ml/kg/day
Otherwise unremarkable
How do you investigate central diabetes insipidus?
Hospitalise for 12-24 hours
Observe water consumption
If it stops drinking - primary polydipsic problem
If it keeps drinking - need to do more
What diagnostic aids are there for central diabetes insipidus?
USG <1.008
Urine osmolality and SG fixed and unchanging
Water deprivation test
Followed by desmopressin response test if needed
Describe the water deprivation test….
- Patient must become dehydrated
- Can take up to 72 hours
- Administer desmopressin once inability demonstrated
- Usually response within 2-12 hours
- Usually USG >1.020 within 4 hours
