Book of Medical Disorders in Pregnancy - Tintash

such as phenobarbitone 30 mg given
orally at 8 hourly intervals is quite
useful.
Medical treatment - The physician
treating thyroid disease should do so in
collaboration with an internist who is
especially interested in obstetrical problems.
The drugs commonly used reduce the
production of thyroxine and include
Carbimazole or (nimorazole), Methyl
thiouracil and potassium perchlorate.
THE first two drugs prevent incorporation
of Iodine into Tyrosine nucleus
by inhibiting the required enzymes,
while the third or last drug interferes
with Iodine trapping mechanism of the
thyroid gland. These drugs can cross the
placental barrier and therefore produce
fetal goitre. This goitre usually disappears
in 1 to 2 weeks after birth. The
fetal goitre may result in respiratory
obstruction. Hypothyroidism can result
from over treatment with these drugs and
this may lead to mental retardation in the
neonate.
Initial dose of carbimazole is 15 milligram
8 hourly by mouth. When the symptoms
are controlled, the dose is reduced
to 10 milligrams, and finally 5 mgs twice
daily, until she becomes euthyroid.
Initial dose of methylthiouracil is 100
mgs hourly by mouth. When symptoms
are relieved 50 mgs 8 hourly is given
and finally 50 mgs daily, till patient is
euthyroid.
Initial dose of Potassium Perchlorate is
250 mgs 8 hourly. When the patient is
euthyroid then 300 mgs daily is given as
a maintenance dose. Side effects such as
fever, rashes on skin, sore throat, agran-
37
ulocytosis etc, may occur. Occasionally
medication may have to be stopped due
to side effects.
It is important that the physician treating
hyperthyroidism in pregnancy constantly
monitors the thyroid status during
treatment. The PBI tests are not reliable,'
therefore, T3, T4 and 1131 red cell
uptake tests should be done. It has been
demonstrated that if the mother is kept
euthyroid, no harm can result to the fetus
by the use of antithyroid drugs. There
may be slight thyroid enlargement, but
this disappears within two weeks after
birth. Some physicians prefer to give 0.1
mg of sodium L-thyroxine at the same
time the antithyroid drug is being given.
The rational is to avoid the risk of
hypothyroidism in the infact. The fetus
starts to produce its own thyroxine
around 20th week of gestation. A critical
level of thyroxine is necessary for
normal development of the fetus. If this
is not available proper brain developpment
cannot occur, and the damage
produced in utero cannot be reversed by
giving thyroid hormone after birth.
Fig3.2: Shows thyroidectomy being
carried out surgically.
Thyroidectomy - Some Physicians
prefer surgery over medical treatment.
Hawe and Francis in (1962) reported
good results with partial thyroidectomy