Page 2649 - Cote clinical veterinary advisor dogs and cats 4th

1354 Insulin, Serum Level

Next Diagnostic Steps to Consider presence of a sinusoidal spleen in this species, Pearls
if Levels Are High which effectively removes the inclusions from Occasionally inclusions may appear atypical
VetBooks.ir further investigation is necessary. Review history is not as efficient at removal, so low numbers of pathologic significance (e.g., parasites). If
and difficult to distinguish from inclusions
erythrocytes. The non-sinusoidal spleen of cats
If a strongly regenerative anemia is present, no
numerous or atypical, consider review by a
of inclusions may be found in the peripheral
for prior splenectomy and current medications.
Consider macrocytosis of poodles (MCV may
range from 90-100 fL). Myelodysplastic syn- blood of healthy cats. clinical pathologist.
dromes are uncommon in veterinary medicine, Drug Effects AUTHOR: Mary Leissinger, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
and in these conditions Howell-Jolly bodies Glucocorticoid therapy or chemotherapeutic
would be accompanied by dysplastic features agents can increase numbers.
and cytopenias in one or more hematologic cell
lines. If myelodysplastic syndrome is suspected, Specimen Collection and Handling
the sample should be submitted for review by Anticoagulated blood sample, as for routine
a clinical pathologist. CBC with blood smear
Important Interspecies Differences Relative Cost: $$ (reported as part of CBC,
Howell-Jolly bodies are generally absent in the and only if excessive)
peripheral blood of healthy dogs owing to the

Insulin, Serum Level

Definition ○ Concurrently increased insulin and sometimes related to factors other than insulin
Insulin is a polypeptide hormone that promotes progesterone concentration in a newly itself. For example, overproduction of insulin-
uptake of glucose by a variety of cell types. diagnosed diabetic intact female dog sug- like growth factor 2 (IGF-2) has been reported
gests diestrus may be causing the insulin in some canine tumors.
Physiology insensitivity. This form of diabetes mellitus
Insulin is produced by pancreatic islet beta-cells. may not require medical management Drug Effects
Normally a rise in blood glucose concentra- post-ovariohysterectomy. Administration of exogenous insulin or insulin
tion (but also growth hormone, amino acid In a hypoglycemic patient antagonists may increase results.
concentration, and others) will cause release of • Overproduction of insulin
insulin to the blood. Major effects of insulin ○ Insulinoma Lab Artifacts
include promotion of myocyte and adipocyte ○ Xylitol toxicosis Presence of patient anti-insulin antibodies may
glucose uptake, increased production of falsely increase or decrease results depending
glycogen in hepatocytes and myocytes, and Next Diagnostic Steps to Consider on test methodology.
decreased lipolysis and proteolysis. Depletion if Levels Are High
of pancreatic beta-cells results in inadequate In a patient suspected to have insulinoma, Specimen Collection and Handling
insulin production (type I diabetes mellitus). abdominal imaging to identify a potential Collect blood into a red top tube at a point
Persistent insulin antagonism (for instance, in neoplasm is warranted. See p. 552. when the patient is hypoglycemic, ideally
hyperadrenocorticism) will initially cause con- < 65 mg/dL (if assessing for insulinoma). Spin
current hyperglycemia and hyperinsulinemia. Causes of Abnormally Low Levels and collect serum, refrigerate or freeze, and
Measurement of insulin in diabetic patients Low levels are expected in a hypoglycemic submit on ice overnight. Plasma from heparin
is not common. Instead, serum insulin is patient or in patients with type I diabetes tubes (green top) or EDTA tubes (lavender top)
usually measured concurrently with glucose mellitus. may be acceptable; check with your lab for
concentration to investigate hypoglycemia in specific guidelines. Hemolysis will interfere with
a patient with suspected insulinoma (functional Next Diagnostic Steps to Consider some assays; clear serum or plasma is preferred.
beta-cell neoplasm). if Levels Are Low
If insulin level or insulin to glucose ratio is low Relative Cost: $-$$
Reference Interval in a hypoglycemic patient, evaluation for other
Varies by laboratory causes of hypoglycemia is warranted. Assuming AUTHOR: Angela Royal, MS, DVM, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
CBC and chemistry panel do not support the
Causes of Abnormally High Levels possibility of hypoadrenocorticism, hepatic
In a hyperglycemic patient insufficiency, portosystemic shunt, sepsis, or
• Expected response to hyperglycemia. If other known causes of hypoglycemia, imaging/
persistent, indicates insulin resistance/ assessment of the patient for neoplasia is still
insensitivity. recommended. Paraneoplastic hypoglycemia is

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