Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (206 page)

   Stimulatory tests should be performed if hypofunction is suspected and suppression tests if hyperfunction is suspected.

   Suppression tests suppress normal glands but not autonomous secretion.

   Patient preparation is particularly important for hormone studies, results of which may be markedly affected by many factors such as stress, position, fasting state, time of day, preceding diet, and drug therapy. These all should be recorded on the laboratory test requisition form and discussed with the laboratory prior to test ordering.

   Appropriate and timely transportation to the laboratory and preparation of specimen are essential.

   No single test adequately reflects the endocrine status in all conditions.

   Multiple gland hypofunction should evaluate the pituitary gland.

   
DIABETES MELLITUS

   Definition

The term “diabetes mellitus” (DM) refers to a group of disorders of abnormal carbohydrate metabolism sharing in common the clinical finding of hyperglycemia. DM is associated with a relative or absolute impairment in insulin secretion, along with varying degrees of peripheral resistance to the action of insulin.

   Overview

DM affects approximately 5% of the world population and 8% of the US population. It is the fourth leading cause of death in the United States. Of the estimated 18 million people with primary DM in the United States, 90–95% have type 2 DM.

   Types and Classification

The recent classification focuses on the underlying pathophysiologic process, rather than descriptions based upon age at onset or type of treatment.

  1.  Type 1: immune mediated, results in an absolute insulin deficiency.

  2.  Type 2: relative insulin deficiency due to abnormalities of both insulin secretion and insulin action. Insulin levels are sufficient to prevent lipid mobilization and ketosis.

  3.  Gestational diabetes: diagnosed during pregnancy. Only 2% of patients with gestational diabetes remain diabetic after delivery. Forty percent of the patients will develop overt diabetes within 15 years, mostly type 2, but occasionally type 1.

  4.  Specific types of diabetes:

a.   Genetic defects of beta cell function

b.   Genetic defects in insulin action

c.   Diseases of the exocrine pancreas, such as pancreatitis, trauma, pancreatectomy, neoplasia, cystic fibrosis (CF), hemochromatosis, and fibrocalculous pancreatopathy

  5.  Associated with endocrinopathies (i.e., Cushing syndrome), drugs (i.e., corticosteroids), or chemicals.

   Who Should Be Suspected?

The clinical onset of diabetes can be acute or insidious, depending both on the degree of insulin deficiency as well as on the intercurrent level of physiologic stress. Patients with the following symptoms and signs should be tested: