OBESITY
OBESITY: Excerpt from Differential Diagnosis in Primary Care
The differential diagnosis of obesity, like that of weight loss, is
best developed using physiology because most cases of obesity are
caused by an absolute increased intake of calories or a relative increased
intake of calories over output of energy. Fluid retention may also be
associated with weight gain.
Increased intake of calories. This type of obesity is due
to an increased appetite. Under this heading are idiopathic obesity,
psychogenic obesity, hypothalamic obesity (due to pituitary tumors and other
lesions affecting the hypothalamus), islet cell adenomas and carcinomas
(causing hypoglycemia and, consequently, a big appetite), early stages of
diabetes mellitus when functional hypoglycemia is common, Cushing syndrome
and exogenous corticosteroids (which increase appetite), and alcoholism,
which stimulates the appetite but which also adds calories in the alcohol
(up to 250 calories per cocktail).
Decreased output of energy. Under this heading should be
listed hypothyroidism and possibly hypogonadism (such as Klinefelter
syndrome), where the motivation to work or exercise may be impaired. Mild
pituitary insufficiency (as in Sheehan or Fröhlich syndrome) may also
cause obesity by this mechanism. Lack of energy in primary growth hormone in
adults may cause obesity. This type of obesity may be occupational (e.g.,
white collar workers) or environmental (i.e., watching television all day).
“Obesity” due to fluid retention. This increase is in
reality an increase in weight from fluid retention. Inappropriate
antidiuretic hormone (ADH) syndromes such as those that occur in carcinoma
of the lung, hypothalamic lesions, and drugs are the most important obscure
causes. Congestive heart failure (CHF), nephrosis, cirrhosis, beriberi, and
myxedema rank as significant among the obvious causes.
Miscellaneous causes. Heredity is a cause of obesity, but
the physiologic mechanism is uncertain.
Approach to the Diagnosis
It would be ridiculous to do a complete endocrine workup on every case
of obesity, but thyroid function studies may be worthwhile. Patients who
fail to lose weight on a strict diet may require hospitalization with
observation. If they still fail to lose weight, a complete endocrine workup
would seem to be indicated.
Other Useful Tests
-
48-hour fast with glucose monitoring (insulinoma)
- Plasma insulin (insulinoma)
- C-peptide (insulinoma)
- Serum cortisol (Cushing syndrome)
- Dexamethasone suppression test (Cushing syndrome)
- Pelvic sonogram (polycystic ovary)
- Chromosomal analysis (Klinefelter syndrome)
- Psychiatry consult
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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