Exotics

Question 1

describe different anatomic components for endocrine in exotics

Answer 1

1. thyroid: role in metabolism and feather growth
   -temperature dependent metabolism
2. parathyroid: calcium regulation and eggshell formation
   -calcium and phosphorous balance
3. pancreas: insulin and glucagon in glucose homeostasis
4. environmental impact on endocrine function!
   -UVB for vitamin D synthesis

Question 2

describe challenges in diagnosing endocrine diseases in birds and reptiles

Answer 2

1. limited reference ranges for hormone levels
2. nonspecific clinical signs

Question 3

describe general principles of treatment strategies for exotics with endocrine disease

Answer 3

1. correcting husbandry: diet, lighting, temperature
   -SUPER IMPORTANT
2. pharmacological interventions not well described
3. different species have very different physiology (good luck)
   -birds: oral versus injectable
   -reptiles: slow metabolism affecting drug dosing
4. prognosis/client education:
   -preventing recurrence through proper care
   -importance of long term management

Question 4

describe hypothyroidism in birds

Answer 4

1. etiology: iodine deficiency, goitrogen exposure
2. clinical signs:
   -lethargy
   -obesity
   -feather abnormalities
3. diagnosis:
   -thyroid hormone levels? not very easy diagnosis
   -TSH stim test is possible but rarely diagnostic because hella expensive; biopsy often needed
   -response to supplementation
   -often diagnosis of exclusion
4. treatment:
   -iodine supplementation
   -trial therapy is often indicated because of problematic diagnosis; start on drug for suspected problem, observe clin signs, stop therapy, observe, etc. up to 3x and conclude if helping or not
   -dietary correction
5. what is means:
   -be aware of its existence; if an animal has a thyroid gland it can malfunction
   -recognize the chief clinical signs!
   -avian hypothyroidism is a questionable diagnosis

Question 5

describe diabetes mellitus in birds

Answer 5

1. etiology: pancreatic dysfunction, obesity, coelomitis?
   -pancreatic insulin content is approx 1/6 that of mammalian pancreas but glucagon content is 2-5x greater so plasma glucagon concentration are 10-50x higher in birds than in mammals
2. clinical signs:
   -PU/PD
   -weight loss despite normal food intake
3. diagnosis: easy
   -BG levels: (fasted >800mg/dL = diagnostic, most present >1000mg/dL)
   -glucosuria
   -pancreatic biopsies recommended but uncommon
4. treatment: tricky
   -insulin therapy (anecdotal use of bovine, porcine, and human recombo; see VIN as best source of info)
   -Mayer likes glipizide in the drinking water!
   -dietary management
   -treat secondary problems

Question 6

describe glucose regulation differences in birds

Answer 6

1. plasma glucose appears largely insensitive to insulin regulation in granivorous species, but raptor species may be more insulin dependent
2. chickens normally have approx 2x the plasma glucose concentration of mammals, experiencing only minor changes during short term and/or prolonged starvation
3. avian glucose regulation is unorthodox and not well understood

Question 7

describe glucagon in birds

Answer 7

1. believed to be a more effective glucose regulator in granivorous species than insulin and some think DM is NOT due to insulin deficiency
2. ducks and chickens withstand surgical removal of pancreas better than mammals = mild and temporarily induced DM
3. chickens appear resistant to diabetogenic drugs (streptozotocin, alloxan), which may indicate that chicken pancreatic beta cells are highly protected

Question 8

describe determinant versus indeterminate layers

Answer 8

determinant: lay a fixed number of eggs in a single clutch regardless of external factors like egg removal or loss
-ex. crow and budgerigars

indeterminant layers: can replace a lost egg by laying another

Question 9

describe reproductive behavior in hens

Answer 9

1. signs:
   -paper shredding
   -nest building
   -hiding under papers
   -seeking dark places
   -pair bonding: regurgitation, copulation, nest box inspection, feeding, mutual preening
   -macaw or amazon parrots may show coordinated territorial defense
2. environmental cues that stimulate repro activity:
   -photoperiod
   -temeprature
   -rainfall
   -vocalizations
   -presence of nesting material
   - +/- presence of mate (real or imagined)
   (can manipulate these to help fix sexual frustration)

Question 10

describe photoperiod

Answer 10

1. the most important environmental cue for repro activity in most avian species
   -cockatiels especially sensitive among psittacines
   -potentially obesity is also very very important in making a chronic egg layer
2. long day length stimulates release of luteinizing hormone-releasing hormone
   -which then promotes gonatotroping (FSH and LH) secretion
   -LH stimulates steroidogenesis
   -FSH: role not well understood in the hen
3. maximal photostimulation occurs with 12-14 hours of light
   -normal egg-laying can occur anywhere from 12-18hrs of light
   -long day length does not need to be continuous as long as exposure to light occurs during this photosensitive phase!

Question 11

do you spay a hen with chronic egg laying?

Answer 11

NO or at the very least do not take ovary out!

1. some will develop a right ovary
2. 90% develop a testicle?? and active spermatogenesis?

Question 12

describe chronic egg laying

Answer 12

1. extremely common
2. often oversimplified regarding management
3. drugs alone without significant changes in the husbandry and environment will ever lead to success
   -can be a frustrating problem so act fast and get buy-in from the owner

Question 13

describe secondary hyperparathyroidism in reptiles

Answer 13

1. etiology:
   -calcium deficiency
   -lack of UVB
   -renal disease
2. clin signs:
   -soft bone
   -deformities
   -tremors
3. diagnosis:
   -radiograph: look for boney changes
   -calcium/phosphorous levels
   –Ca:Ph ratio (2:1 = ideal)
   -hormone assays: vitamin D
   -environmental and husbandry history is very important!
4. treatment:
   -calcium supplementation
   -UVB provision

do NOT call it metabolic bone disease!! too broad of a term that includes too many conditions

most common scenario:
-decrease in plasma calcium concentration stimulates the parathyroid glands to release PTH which results in the release of cytokines from osteoblasts, activating osteoclasts that resorb bone to correct the plasma concentration
-over time this reduces bone density, leading to secondary disease conditions

-BUT TOTAL CALCIUM CAN BE NORMAL AND CAN STILL HAVE SO CHECK WITH IONIZED CALCIUM!!! (if total Ca is low = really really bad)

Question 14

describe management of secondary hyperparathyroidism

Answer 14

1. correct underlying issue
2. nutrition, UVB exposure
3. usually will take months
4. fair prognosis