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Thyroid Function Assessment
Using a Cost-Effective and Time-Efficient Testing Algorithm
New Thyroid Function
Screening Cascade
Bronson Laboratory Services introduces
a new laboratory testing cascade for the
initial screening and diagnosis of thyroid
disease in nonhospitalized patients.
The cascade uses an algorithmic approach
beginning with thyroid stimulating
hormone (TSH). Further tests are
performed automatically, at an additional
charge, as illustrated in this flowchart:
Nonhospitalized patients
Not on thyroid replacement
Without known or suspected
pituitary disease
TSH
Low TSH
<0.10 mIU/L
Borderline
low TSH
0.1-0.26 mlU/L
Normal TSH
0.27-4.2 mlU/L
High TSH
>4.2 mlU/L
Suspect
Hyperthyroidism
Free T4
to evaluate
for possible
Hyperthyroidism
No further
testing unless
clinically
indicated
Suspect
Hypothyroidism
Free T4
and
Thyroid
peroxidase
antibodies
Free T4
fT4 <2.0 ng/dL
fT4 2.0 ng/dL
or greater
Total T3
to evaluate
for possible
T3 toxicosis
Consistent
with primary
Hyperthyroidism
Monitoring Patients on
Thyroid Replacement
The complete thyroid screening
cascade is not designed for monitoring
patients receiving thyroid replacement
therapy. For monitoring, TSH and/or free
T4 should be ordered individually.
Patients on a stable dose of thyroid
medication may be monitored with TSH
alone. After initiating thyroid replacement therapy or changing dosage, free
T4 levels should be followed until TSH
levels stabilize (3-6 weeks).