Thyroid dysfunction in infertile women.

OBJECTIVE

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

DESIGN

A retrospective case-control study.

PLACE AND DURATION OF STUDY

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

PATIENTS AND METHODS

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).

RESULTS

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).

CONCLUSION

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.