Endocrine disease in small mammals and exotic species

• Calcium metabolism in birds and reptiles overview

  If you increase calcium in the diet it might not increase blood calcium levels.

  Vitamin D is needed to absorb dietary calcium from the intestines.

  Vitamin D2 is found in plants, unlike mammals, birds and reptiles can not easily use Vitamin D2. They need to use active vitamin D3.

  UV-b and heat are needed for reptiles to convert D2->D3.
• Calcium metabolism - bearded dragon example

  Three things are needed for calcium metabolsim in a bearded dragon:

  • UV-B light - doesn’t penetrate through glass.
  • Heat
  • Correct diet and supplements.
• Calcium metabolism - herbivorous reptiles

  Always need supplements as diets in captiviity often have an inverse Ca:P ratio and/ or constrain phytates and oxalate which may further reduce calcium availability in the diet. Which doesn’t happen in the wild.
• Calcium metabolism - Insectivorous reptiles

  Always require supplements. Captive-raised insects often have an inverse Ca:P ration, as they are not in the environment they would be in the wild.
• Calcium metabolism - carnivorous reptiles

  Do not need supplements id they’re are fed whole prey. If fed all-meat diet or neonatal prey then they could have an inverse Ca:P ration and then they require supplements.
• Calcium metabolism - birds

  Similar to reptiles

  Hypocalcaemia is often due to inappropriate diet and husbandry.

  UV-B is essential for some birds (e.g. African Grey Parrot) but not all.

  Egg-laying like most reptiles, but multiple clutching in birds can cause hypocalcaemia e.g. laying hens.
• Calcium metabolism - dietary supplements needed in birds

  Insectivorous birds:

  • Always needs supplements. Captive-farmed insects have an inverse Ca:P ration.

  Parrots:

  • Supplements are not needed if their diet is correct. Seed-based diets are deficient in calcium and vitamin D so will need supplements then while you try and put them on the correct diet.

  Carnivorours birds:

  • Don’t need supplements if are fed whole prey. All-meat diet, or over enthusiastic eviscerating will result in inverse Ca:P
• Calcium metabolism - rabbits overview

  Same hormones involved (PTH, calcitonin and vitamin D3).

  Rabbit calcium metabolism differs to most other mammals because they can absorb dietary calcium from the gut using bath an active and passive absorption methods.
• Calcium metabolism in rabbits - active absorption

  Vitamin D2 -> D3 in the kidney by PTH if have low serum calcium, this stimulates intestinal absorption.
• Calcium metabolism in rabbits - passive absorption

  Absorbed across the gut wall, vitamin D is not required (unlike other mammals). There is no feedback mechanism.
• Calcium metabolism in rabbits - excretion and tolerance

  So if they have calcium levels in their diet, they will absorb to much calcium.

  If high in diet = high serum calcium.

  In rabbits calcium excretion is mostly via kidney. They can excrete up to 60% ingested calcium in their urine.

  So they have good tolerance of high levels of dietary Ca2+.
• Calcium metabolism - guinea pigs

  Like rabbits, guinea pigs do not regulate calcium absorption from the gut.

  Guinea pigs absorb around 50% of the calcium they ingest.

  If fed excess calcium, the excess absorbed calcium is excreted through the urinary tract.
• Non-specific Clinical signs of calcium imbalance in small mammals.

  Non-specific clinical signs of endocrine disease include PUPD, anorexia, lethargy/weakness and weight loss.
• Specific clinical signs of calcium imbalance in small mammals.

  Pancreatic adenomas:

  • Hindlimb weakness, nausea, dazed expression, ataxia, collapse and coma.

  Hypercalcaemia:

  • Dysuria, pollakiuria, haematuria, thick beige-brown urine, urine staining, abdominal pain.

  Reproductive system:

  • Swollen vulva, symmetrical hair loss, palpable cystic ovaries, anaemia.
• Calcium imbalance in reptiles clinical signs - metabolic bone disease

  Anorexia

  Lethargy/ weakness

  Abnormal gait

  Bone deformities and swellings e.g. mandible, long bones.

  Pathologic fractures.

  Constipation (smooth muscle isn’t able to contract properly), egg binding, cloacal prolapse.

  Dysecdysis

  Muscle tremors/ fasciculations and tetany.
• Calcium imbalance in birds clinical signs - non-specific

  PUPD

  Anorexia

  Lethargy/weakness
• Endocrine problems in birds clinical signs - specific

  Dyspnoea, regurgitation and dysphasia are seen with thyroid goitres in hyperthyroidism.

  Weakness, ataxia, bone deformity/fractures, tetany and seizures are common in parathyroid disease (MBD)
• Common endocrine diseases in small mammals - ferret

  Hyperadrenocorticism

  Insulinoma

  Persistent oestrus

  Diabetes mellitus

  Hypothyroidism

  Phaeochromocytoma
• Common endocrine diseases in small mammals - guinea pigs

  Cystic ovaries

  Urolithiasis (hypercalcaemia)

  Alopecia (during pregnancy/lactation)

  Diabetes mellitus

  Hyperthyroidism

  Hyperadrenocorticism.
• Common endocrine diseases in small mammals - rabbits

  Bladder sludge (hypercalcaemia)

  Urolithiasis (hypercalcaemia)

  Hypocalcaemia

  Diabetes mellitus

  Adrenal gland tumours.
• Common endocrine diseases in small mammals - other rodents

  Diabetes mellitus e.g hamsters, degus, chinchillas, gerbils. Do give insulin to these.

  Hyperadrenocorticism e.g. hamsters, gerbils

  Pituitary gland adenoma e.g. rats.
• Insulinomas - ferrets

  Pancreatic adenomas in ferrets.

  Hyperinsulinamia -> hypoglycaemia.

  Clinical signs stop in response to food or glucose, do go completely back to normal when fed correctly.

  Average occurrence 2-8 years.

  Feeding processed dry foods high in carbohydrate might stimulate the development of tumours.
• Common causes of hypercalcaemia in rabbits

  Increased dietary intake e.g. Alfalfa hay.

  Renal disease

  Primary hyperparathyroidism

  Hypervitaminosis D

  Osteomyeltitis

  Paraneoplastic syndrome e.g. thymoma.
• Other causes of bladder sludge in rabbits

  Dehydration (really hot temperature or no access to water).

  Reduced movement e.g. arthritis, obesity, and confinement.

  Not fully voiding bladder when urinating e.g. partial obstruction, spondylosis, abdominal pain.
• Other consequences of hypercalcaemia - persistent hypercalcaemia

  In rabbits persistently raised calcium may result in:

  • Dystrophic calcification, particularly in the aorta and kidneys e.g. kidney damage.
  • Hyper-mineralisation of the skeleton.
• Hypocalcaemia in rabbits

  Calcium deficient diet leads to reduced serum calcium and increased PTH secretion.

  Leads to demineralisation of the skull, teeth and skeleton.

  Spine fractures and dental disease are commonly found.

  PTH also increases RBC osmotic fragility causing anaemia.

  Hypocalcaemia may be seen before parturition.
• Common endocrine disorders in reptiles - overview

  Hypocalcaemia/metabolic bone disease:

  • Nutritional secondary hyperparathyroidism (NSHP)
  • Renal secondary hyperparathyroidism (RSHP)

  Hypercalcaemia

  Hypothyroidism and hyperthyroidism.
• Common endocrine disorders in reptiles - nutritional secondary hyperparathyroidism

  Decrease in calcium in the diet (or an increase in phosphate).

  • Lack of UV-B light
  • Poor environmental temperatures
  • Decreased vitamin D in the diet.

  Increase in PTH to increase the calcium in the bloods.

  PTH-gland hyperplasia.

  Calcium mobilised from the bone.
• Common endocrine disorders in reptiles - renal secondary hyperparathyroidism

  Decreases in phosphorous excretion so an increase in phisphprois in the blood:

  • Over supplementation of Vitamin D3
  • Malnutrition
  • High protein diet
  • Kidney infections

  Reversed Ca:P ration

  Increase in PTH to increase the calcium in the blood

  Parathyroid gland hyperplasia

  Calcium mobilised from the bone.
• Hypercalcaemia in reptiles and birds - overview

  Most common physiological problem in reproducing females.

  Para-neoplastic Hypercalcaemia is not reported.

  Can be caused by hypervitaminosis D and excessive dietary calcium intake in both reptiles and birds.

  In reptiles particularly, it can also be primary hyperparathyroidism and Osteolytic bone lesions.
• Hypercalcaemia in reptiles and birds - consequences of prolonged hypercalcaemia

  Soft tissue mineralisation where calcium deposits occur.

  Nephrocalcinosis -> visceral and articulate gout when uric acid is deposited in the joints.
• Uroliths in exotics - overview

  Many reptiles do not have bladders, but tortoises do and they commonly get uroliths.

  Unlike rabbits and guinea pigs though, they are not linked to calcium metabolism.

  Uroliths in tortoises consists of uric acid rather than calcium,.
• Common endocrine disorders in birds - overview

  Medullary hyperostosis

  Hypocalcaemia (NSHP and RSHP)

  Hypercalcaemia

  Thyroid hyperplasia (goitre) due to dietary iodine deficiency (budgies particularly).
• Common endocrine disorders in birds - medullary hyperostosis

  Hyperostosis = calcium storage in medullary bone changes the pneumatic appearance to solid and dense material.

  Egg laying places huge demand on calcium supply.

  Begins at 6 weeks prior to egg laying.

  Hyperostosis is reported in both normal and abnormal female psittacine birds.

  Under the influence of oestrogen and vitamin D.

  Where calcium/ vitamin D3 is insufficient, a moth-eaten appearance often occurs.
• Common endocrine disorders in birds - calcium metabolism in birds compared to reptiles


  In birds, calcium metabolism during egg reduction appears to be similar to reptiles, only they produce eggs more frequently.

  Hypocalcaemia in birds has the same clinical signs as reptiles, plus feather plucking due to bone and joint pain. Breeding females also show egg-binding, soft-shelled eggs and infertility.
• Diagnostic tests for endocrine disease in exotics - blood test overview

  Haemotology and biochemistry, glucose readings, ionised calcium, hormone testing.

  Blood tests can help how you the body system involved e.g. kidney disease.

  Sex hormones can be measures e.g. hyperadrenocorticism disease in ferrets.

  Other hormones e.g. thyroid in any species.

  Vitamin and mineral are hard to test, often only history and husbandry can indicate these deficiencies.
• Diagnostic tests for endocrine disease in exotics - blood test - calcium testing

  Total calcium:

  • Measures all three. Therefore, if change albumin levels, total calcium will change, pH can also change total calcium (affects protein binding). So total calcium is not reflective of true calcium status.

  Ionised calcium:

  • Also called free calcium, is the most active form. Most specific way to look at calcium levels in birds and reptiles.
• Diagnostic tests for endocrine disease in exotics -Urinalysis in birds and reptiles

  Not very useful to assess kidney function as kidney does not dilute the urine.
• Diagnostic tests for endocrine disease in exotics - urinalysis in rabbits and guinea pigs

  Manual urine specific gravity can help assess kidney function.

  Can perform a dipstick to look for blood e.g. urolith or cystitis.

  Hard ti obtain a sterile sample for culture, cystocentesis has a high risk for peritonitis in hind gut fermenters.
• Diagnostic tests for endocrine disease in exotics - radiographs/CT

  Can assess bone density, bone deformities, fractures, tissue mineralisation.

  Can indentify eggs in birds and reptiles, cystic ovaries in guinea pigs and bladder sludge and/or urolithiasis in pigs and rabbits.