Hyperthyroidism is the condition where the body produces a low amount of thyroid hormone, whereas hypothyroidism is when the body overproduces thyroid hormone. Overt hyper- or hypothyroidism in women can affect fertility.
Prior to starting their infertility treatment, female patients at Neway Fertility will be tested for thyroid disease.
Hypothyroidism and Hyperthyroidism
According to the American Thyroid Association women are five to eight times more likely than men to have thyroid problems. Overt hyper- or hypothyroidism in women can affect fertility and pregnancy and can be suspected on clinical grounds and is diagnosed by elevated or decreased TSH levels as defined by the laboratory measuring this hormone i.e. specific reference range for a specific laboratory (for example Quest Diagnostics: normal range 0.4 – 4.5 mIU/L). Therefore all women seeking infertility treatment at Neway will be tested for thyroid disease. In case of overt hypo- or hyperthyroidism the patient will be referred to an endocrinologist with special expertise in thyroid disease. Infertility treatment will be initiated once the thyroid condition will have been treated appropriately.
Subclinical hypothyroidism (SCH)
There are insufficient data to conclude that SCH is clearly associated with infertility. The deleterious effects of overt hypothyroidism are well established, but even subclinical hypothyroidism in pregnant women can affect neuro-developmental processes and can cause cognitive impairment in the developing embryo, fetus and therefore in the future child. The American Society of Reproductive Medicine, the Association of American Clinical Endocrinologists and the Endocrine Society recommend levothyroxine replacement in all women with SCH defined as TSH > 2.5 mIU/l in first trimester, regardless of thyroidperoxidase antibody (TPO ab) status. Therefore and as stated above all female patients seeking pregnancy at Neway will be tested for serum TSH levels.
If the TSH level is < 2.5 mIU/l no intervention is necessary and it is recommended to repeat testing for TSH after 12 months. If TSH level is between 2.5 mIUml and 4 mIU/L the TSH test will be repeated together with free T4 and TPO ab status will be assessed. In case the patient is TPO negative and repeat TSH is > 2.5 mIU/l but < 4 mIU/L no intervention is necessary in the non-pregnant state and it is recommended to repeat testing in 6 months. If the patient becomes pregnant TSH will be remeasured with the second repeat test of the pregnancy hormone human chorionic gonadotropine (hCG) . If TSH is > 2.5 mIU/L the patient will be started on 25 microgram or higher of levothyroxine (depending on TSH level) and TSH will be reevaluated in 30 days.
If patient is TPO ab positive in the non-pregnant state, she will be started on levothyroxine 25 micrograms. If the TPO positive patient becomes pregnant TSH will be remeasuered with the second repeat testing of the pregnancy hormone hCG and leveothyroxine might be readjusted depending on the TSH level. In patients taking thyroid medication TSH will be remeasured in 30 days from the time point of the second hCG measurement as pregnancy induced alterations in blood components can alter the availability of thyroid hormone to the developing embryo.
If TPO ab status is equivocal no intervention is necessary in the non-pregnant state and TSH, free T4 and TPO antibody will be remeasured in 6 months. If the patient becomes pregnant TSH will be measured again with the second repeat test of the pregnancy and thyroid medication will only be given if the TSH is > 2.5 mIU/L.