WHAT A HEALTH
PROVIDER SEES
G estational D iabetes
J
enna is pregnant and has her blood glucose checked during
her regular obstetrical visits. During one of her tests, her fasting
blood glucose is greater than normal. She fears that she might have
gestational diabetes
, a type of diabetes that affects about 4% of
pregnant women, representing about 135,000 new cases in the
United States each year. Although the exact cause is unknown, it's
thought that hormones released by the placenta during pregnancy
block the action of the mother's insulin (that is, cause insulin
resistance).
The
mother's
pancreas
secretes
more
insulin than usual but not enough to remove glucose
adequately. The increased blood glucose and
other nutrients stimulate the baby’s pancreas
to hypersecrete insulin. As a result, the baby
gains additional fat during development, which
presents complications for delivery, low blood
glucose at birth, and risk for obesity and
type II diabetes in the mother.
Jenna's physician orders a one-hour oral glucose tolerance test
(OGTT), usually done between weeks 24 to 28. To prepare for this
test, Jenna fasts for 8 to 12 hours prior to the test. A technician takes
a blood sample and then gives her a high-glucose drink (~50 g). She
has blood drawn 1
hour later. Her blood glucose level is higher than
normal (see the table below), so the physician orders a 3-hour OGTT.
Jenna prepares for this test in the same way but drinks a higher-
glucose drink (100 g) and has blood drawn at 1-hour intervals for 3
hours. When her test results show higher-than-normal responses,
her physician diagnoses gestational diabetes.
For treatment, Jenna goes on a restricted carbohydrate diet,
begins a new exercise program, and uses a blood glucose meter to
monitor her blood glucose daily. Also, because Jenna may require
two or three times the normal insulin levels, she requires daily insulin
injections. This treatment will continue until she gives birth. For
many women, gestational diabetes goes away after birth, but some
women become diabetic permanently.
Normal blood
Other blood
Test
glucose (mg/dL)
glucose (mg/dL)
Diagnosis or treatment
Fasting
< 100
100-126
A dm inister G TT
1-hour O G TT
< 140
>140
Gestational diabetes; m ay
(50 g glu cose —»
take 3-hour test and/or
blood sam ple
in 1 hour)
retake the test in 4 w eeks
3-hour O G TT
Fast
< 95
Values greater than
Gestational diabetes
(100 g glu cose —»
1
< 180
norm al
blood sam ple at
2
< 155
1,2, and 3 hours)
3
< 140
1. W hy does hypersecretion of insulin by the fetus cause the b aby to gain excess w eight?
2. W hy m ight Jen n a require two or three tim es the normal insulin levels?
1.
How
is human growth hormone secreted, and
what are its effects?
2.
How
do the hypothalamus and pituitary gland
interact to control the secretion of thyroid hor-
mone?
3.
What
is the effect of parathyroid hormone on
blood calcium levels?
4.
How
does the pancreas help control blood glu
cose levels?
268 CHAPTER 9
The Endocrine System
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