Page 553 - Small Animal Clinical Nutrition 5th Edition

572 Small Animal Clinical Nutrition

VetBooks.ir Table 29-8. Clinical signs associated with hypothyroidism and hyperthyroidism. Hypothyroidism
Clinical signs
Hyperthyroidism
Appetite
Nervous, hyperactive to lethargic, excess
Lethargy, mental dullness, inactivity, cold intolerance
Behavior Increased to decreased Normal to decreased
vocalization, aggressive, heat intolerance
Coat Dry/greasy/patchy alopecia/unkempt Dry/sparse (endocrine alopecia), seborrhea
Eyes Normal Normal or corneal lipid deposits, corneal
ulceration/uveitis
Heart rate/rhythm Increased with possible dysrhythmias Normal to decreased with possible dysrhythmias
Neck Normal/mass Normal/mass
Neuromuscular Weakness, tremors, ventriflexion of head, Seizures, ataxia, circling, vestibular signs, weakness,
muscle wasting knuckling, facial nerve paralysis
Respiratory Panting, respiratory distress, Normal
dysphonia (dogs)
Skin Normal Hyperpigmentation
Stools Bulky to diarrhea Constipation to diarrhea
Thirst Increased Normal to decreased
Urine Excess urination Normal
Vomiting Possible No
Weight Normal to decreased Normal to increased
Other Reproductive dysfunction Reproductive dysfunction, poor growth

glycemia is common, even in well-controlled diabetics. Most for glucose determination. The marginal ear vein prick tech-
owners are happy with their pet’s response to insulin treat- nique for blood sampling can be used in diabetic cats to mini-
ment if serum fructosamine concentrations can be kept mize problems with stress-induced hyperglycemia. Home
between 350 and 450 µmol/l. Values greater than 500 µmol/l monitoring of blood glucose concentrations using the margin-
indicate inadequate control of the diabetic state and values al ear vein prick technique is also a viable option. Details on
greater than 600 µmol/l indicate serious lack of glycemic con- adjustment and in-depth analysis of serial glucose curves are
trol. Serum fructosamine concentrations in the lower half of provided elsewhere (Feldman and Nelson, 2004, 2004a).
the normal reference range (i.e., <300 µmol/l) or below the
normal reference range should raise concern for significant FELINE HYPERTHYROIDISM
periods of hypoglycemia in diabetic dogs and cats. Increased
serum fructosamine concentrations (i.e., >500 µmol/l) suggest Hyperthyroidism is a clinical condition that results from exces-
poor control of glycemia and the need for insulin adjustments, sive production and secretion of thyroxine (T ) and triiodothy-
4
but do not identify the underlying problem. ronine (T ) by the thyroid gland. Hyperthyroidism is the most
3
common endocrine disease affecting cats. The first clinical
Serial Blood Glucose Curves reports appeared in the late 1970s and early 1980s (Peterson et
Serial blood glucose curves are indicated during the initial reg- al, 1979; Holzworth et al, 1980). Disease prevalence has been
ulation of newly-diagnosed diabetic dogs and cats and whenev- estimated at one in 300 from necropsy findings (Ferguson,
er an adjustment in insulin therapy is deemed necessary after 1993). In a 1993 survey conducted at the Animal Medical
reviewing the history, physical examination, changes in body Center in New York City,approximately 22 cats with hyperthy-
weight and serum fructosamine concentration. Results of the roidism were identified monthly (Broussard et al, 1995). It is
serial blood glucose curve provide guidance when adjusting the unclear whether the prevalence of hyperthyroidism continues
insulin treatment regimen, unless blood glucose measurements to escalate; however, there is no doubt that feline hyperthy-
are unreliable because of stress, aggression or excitement. roidism is now commonly recognized throughout the world
Reliance on history, physical examination, body weight and and is one of the most frequently diagnosed diseases in small
serum fructosamine concentration to determine when a blood animal practice.
glucose curve is needed helps reduce the frequency of perform- In contrast, hyperthyroidism is uncommon in dogs and is
ing blood glucose curves, reduces the number of venipunctures caused by functional thyroid adenomas and carcinomas, not
and shortens the time the dog or cat spends in the hospital, adenomatous hyperplasia as typically occurs in cats (See
thereby minimizing the patient’s aversion to these evaluations below.) (Feldman and Nelson, 2004d). Thyroid carcinomas
and improving the chances of obtaining meaningful results are highly malignant tumors that spread quickly in dogs.
when a blood glucose curve is needed. Thyroid carcinoma should always be assumed in any dog
When assessing glycemic control, the insulin and feeding diagnosed with hyperthyroidism until histopathologic evalu-
schedule used by the owner should be maintained. The dog or ation of the thyroid mass proves otherwise. Diagnosis is based
cat should be dropped off at the hospital early in the morning, on presence of clinical signs similar to those seen in hyperthy-
and blood obtained every one to two hours throughout the day roid cats (See below.), identification of a thyroid mass with