Hypothyroidism is treated by replacing the deficient thyroid hormone.
Synthroid (a synthetic thyroxine compound) is the most common
and usually the best treatment. It allows a woman to convert circulating
T4 (thyroxine) to the more active metabolite thyronine (T3) within
the cells of the body.
Desiccated thyroid extract differs from thyroxine compounds since
it also contains thyronine (T3). The amount of T3 in the extract
is greater than that normally secreted by the thyroid gland so
these medications can be counterproductive in terms of treatment
for ovulatory dysfunction.
Synthroid is typically started at a low dose (25-50 mcg per day).
The dose of medication is adjusted as needed according to bloodwork
obtained 4-8 weeks after a change in dose. The final dose required
is dependent on the initial degree of hypothyroidism.
Once stabilized (euthyroid) on medication a sensitive TSH assay
should be checked regularly (typically at least once a year) for
all infertility patients. Testing is more often if the women has
had recent onset thyroiditis since her own thyroid function may
continue to deteriorate with the progression of thyroiditis.
Overtreating a patient with hypothyroidism or providing thyroid
hormone replacement empirically for a euthyroid patient is potentially
harmful. Hyperthyroidism (even if through overtreatment with medication)
is associated with osteoporosis (decreased bone mineral content).
Thyroid hormone stimulates bone resorption to decrease overall
bone mineral content. The mechanism for the increased bone resorption
appears to involve direct effects of thyroid hormone on the bone
as well as effects involving vitamin D, calcitonin and parathyroid
hormone.
Hypothyroidism in pregnancy should be treated with medication.
Careful monitoring with monthly TSH concentrations for the first
trimester and every few months thereafter is recommended (often
increased medication is required due to increased circulating
blood volume in pregnancy). Hypothyroidism in pregnancy has been
associated with preeclampsia, intrauterine
growth retardation and possibly spontaneous abortions (miscarriages).
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