3
Figure
1B.
Thyroid
Physiology
During
Pregnancy
Conception
Week
5
Week
10
Week
20
Birth
Fetal
Thyroid
Hormone
Production
Fetal
Dependency
on
Maternal
Thyroxine
T
4
Degradation
by
Placental
Type
3
Deiodinase
Renal
Iodine
Clearance
Physiologic
alterations
of
serum
TSH,
TT3,
TT4,
FT4,
and
thyroid
antibody
concentrations
are
expected
from
the
effects
of
HCG,
estrogen,
and
other
factors
during
pregnancy.
