Subclinical hypothyroidism and thyroid autoimmunity in women with infertility.

OBJECTIVE: To determine the prevalence of different subclinical hypothyroidism (SH) grades and thyroid autoimmunity (TAI) in infertile women.
DESIGN: Retrospective study. Setting. Endocrinology division of a public hospital in Argentina. PATIENTS: Group I comprised 244 women consulting on infertility (>1 year without pregnancy); Group C (controls) comprised 155 healthy women with confirmed fertility. INTERVENTION: Thyroid-stimulating hormone and thyroid peroxidase antibodies were measured in all patients, and a thyrotropin-releasing hormone (TRH) stimulation test was performed in 71 patients to diagnose SH grade 1. The pregnancy rate in hypothyroid women on levothyroxine treatment was also evaluated.
RESULTS: SH was diagnosed in 13.9% of the patients in Group I and in 3.9% of Group C (p < 0.002). The TRH stimulation test was useful to detect SH grade 1 in 12.7% of the infertile patients. Patients with precocious ovarian failure, tubal disturbances and ovulatory dysfunction presented higher SH rates (40.0, 18.2 and 15.4%, respectively) than control patients (p < 0.0001, p < 0.002 and p < 0.003). No significant difference in TAI prevalence was shown in Group I relative to Group C. Pregnancy rate of 44.1% was achieved under levothyroxine treatment.
CONCLUSIONS: We observed a higher prevalence of SH, but not of TAI, in patients with infertility. Our results support thyroid screening in women with reproductive failure.