2
Key Points
Î Pregnancy has a profound impact on the thyroid gland and its function.
Î During pregnancy, the thyroid gland increases in size by 10% in iodine
replete countries, but by 20%–40% in areas of iodine deficiency.
Î Production of the thyroid hormones, thyroxine (T4) and triiodothyronine
(T3), increases by nearly 50%, in conjunction with a separate 50%
increase in the daily iodine requirement.
Î These physiological changes happen seamlessly in healthy women,
but thyroid dysfunction can occur in many pregnant women due to
pathologic processes.
Î Furthermore, other thyroid illnesses such as nodular disease and
thyroid cancer are occasionally detected during pregnancy, and may
require treatment.
The American College of Physicians' Guideline
Grading System
Quality of Evidence
Strength of Recommendation
Benefits clearly outweigh
risks and burden or
risks and burden clearly
outweigh benefits
Benefits finely balanced
with risks and burden
H = High
S = Strong W = Weak M = Moderate
L = Low
I = Insufficient evidence to determine net benefits or risks
Reprinted, with permission, from e Development of Clinical Practice Guidelines and Guidance
Statements of the American College of Physicians. Ann Intern Med 2010;153:194–199.
