Thyroid dysfunction in infertile women

To determine the frequency of thyroid dysfunction in infertile women referred for thyroid evaluation.

A retrospective case-control study.

This study was carried out at Centre for Nuclear Medicine (CENUM), Mayo Hospital, Lahore, from July 2003 to December 2006.

Age matched infertile (n=140 each) and fertile women (n=152 each) referred to CENUM for thyroid evaluation were investigated for incidence of hyperthyroidism (TSH < 0.03 mIU/L), hypothyroidism (TSH < 0.03 mIU/L) and thyroid autoimmunity (antithyroid peroxidase antibody titer>20 IU/L). Serum free T4 (FT4), free T3 (FT3) and antithyroid peroxidase antibody (TPO-Ab) was determined by radioimmunoassay (RIA) and TSH by immunoradiometric assay (IRMA).

Most of the infertile women (89.3%), like control women (93.4%), were euthyroid. The difference of overall thyroid dysfunction was not statistically significant in infertile and control women (10.7% vs. 7.9%; p=0.395). The same was true for incidence of hyperthyroidism (4.3% vs. 5.3%; p=0.701) as well as hypothyroidism (6.4% vs. 2.6%; p=0.104). In infertile women, the incidence of hypothyroidism (6.4%) was slightly higher as compared to hyperthyroidism (4.3%). In euthyroid women of both groups, mean FT4, FT3 and TSH levels were significantly higher (p < 0.05) in infertile women and double number of them had serum TSH>2.5 mIU/L compared to fertile women (31.2% vs. 15.6%; p<0.01). Similarly, more infertile women were TPO-Ab positive (titer>20 IU/L) than control women (7.2% vs. 1.4%; p < 0.05).

Increased incidence of high normal TSH and raised TPO-Ab titer indicate relatively more frequent occurrence of compensated thyroid function in infertile women than normal women of reproductive age. This necessitates considering them a subgroup of women in which all aspects of pituitary-thyroid axis should be thoroughly investigated than merely TSH testing.