Endocrine Abstracts

Introduction: It is known that thyroid disorders can influence menstrual cycle, but subclinical hypothyroidism (SH), as cause of ovulation disorders and luteal deficiency (LD) in particular,is underestimated. Monitoring women’s cycles, according to the Billings Ovulation Method (BOM), can allow a precise timing for hormonal evaluation and diagnose LD. Usually, a basal TSH value of 2.5 mg/ml is considered as cut-off for a good luteal function, but alone cannot identify all cases of SH. In order to verify the sensitivity of TSH dynamics, we have performed TRH test (200 mg iv) in patients with LD, stratifying women according to different ranges of basal TSH values.

Methods: We enrolled 65 women, 20–45 ys, consulting our Centre aimed to learn the BOM for achieving or spacing pregnancy. 40 exhibited an history of infertility. LD was diagnosed by a shortened post-Peak phase length (<11 days) and/or low progesterone (P) levels on the 6th or 7th days after the “mucus peak”. SH was diagnosed with TSH peak >15 mcU/ml after TRH administration (normal basal TSH range: 0.4–3.2 mg/ml, by ECLIA). RESULTS: According to basal TSH levels, patients were divided in 3 groups: group A (n=17, 0.8–1.4 mg/ml), group B (n=20, 1.5–2.4), group C (n=28, 2.5–6.5). An increased TSH response was observed in 3/17 patients of group A, 14/20 of group B, 27/28 patients of group C. In the overall group, the evidence of thyroid autoantibodies was 23% and therefore we escluded auto-immune mechanism as cause of ovarian dysfunction. Mean progesterone levels were in the low-normal range in all groups (mean±S.E.M: 6.8±1.7 in group A, 10.5±2.3 in group B, 8.5±0.1 in group C).

Conclusion: These data suggest that SH has an important impact on luteal function; BOM can be effective for screening these situations and give rise a useful tool in diagnostic and therapeutic options in subfertile couples. Dynamic TSH evaluation can allow to diagnose SH,even in presence of normal TSH basal levels.