P-684 Subclinical hypothyroidism and ovarian reserve indices in women with normogonadotropic anovulation
Authors: Baran R , Babczyk D , Jach R , Gawron I 
Published: June 2023

Abstract

Study question
Does subclinical hypothyroidism (SCH) affect ovarian reserve indices in women with Polycystic Ovary syndrome (PCOS) or other forms of Hypothalamic-Pituitary-Ovarian Axis Dysfunction (HPOD)?

Summary answer
SCH increases Anti-Müllerian hormone (AMH) concentration, but has no influence on Follicle-stimulating hormone (FSH).

What is known already
In PCOS, anovulation is caused by the arrest of growing follicles due to increased frequency and amplitude of luteinizing hormone (LH) pulses, resulting in increased number of pre-antral and antral follicles, and concentration of AMH. In other cases of HPOD, the causes of anovulation are more diverse and have not yet been clearly identified. Thyroid hormones can modify the function of the HPO axis, affecting the maturation of follicles. While overt hypothyroidism is treated to improve ovulation and fertility, the effect of subclinical hypothyroidism (SCH) and the presence of circulating antithyroid antibodies (ATA) on ovarian function is uncertain.

Study design, size, duration
A prospective cohort tertiary single-center study (consent no. 1072.6120.172.2022) included women aged 18-45, examined due to menstrual disorders and/or infertility, from July to August 2022. Only women without previously diagnosed thyroid dysfunction were included. All enrolled women gave informed written consent to participate in the study.

Participants/materials, setting, methods
Women underwent routine gynecological examination and pelvic ultrasound. Blood sample was tested for AMH, FSH, Luteinizing hormone (LH), Thyroid-stimulating hormone (TSH), anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG) antibodies concentrations. The Rotterdam-ESHRE-ASRM criteria were used to diagnose PCOS and its phenotypes. HPOD was diagnosed according to WHO classification. SCH was defined as TSH &gt; 2.5 uIU/ml with normal thyroid function. The above parameters within subpopulations were calculated using regression analysis, Kruskal-Wallis and post-hoc tests.

Main results and the role of chance
The study included 51 euthyroid women aged 18-40. PCOS was diagnosed in 42/51 (82.35%) women, including PCOS-A phenotype in 31/51 (60.78%), PCOS-B in 5/51 (9.8%), PCOS-D in 6/51 (11.76%) women, and HPOD in 9/51 (17.65%) women. There was a significant positive correlation between the concentration of TSH and AMH in the studied population - with the increase of TSH value, the concentration of AMH increased (r = 0.4, p = 0.0035). The mean AMH concentration significantly differed between the groups and equaled to 55.4, 39.4, 31.1, 24.0 pmol/l in PCOS-A, PCOS-B, PCOS-D and HPOD (p = 0.05), respectively. The mean anti-TPO concentration was significantly different between the groups and was equal to 18.2, 19.0, 14.6, 10.9 U/ml in PCOS-A, PCOS-B, PCOS-D and HPOD (p = 0.05), respectively. There was no significant difference in FSH, LH, TSH, anti-TG concentrations between the groups.

Limitations, reasons for caution
The limitations of the study are small study group and single-center nature.

Wider implications of the findings
SCH increases the concentration of AMH, which in PCOS may exacerbate the symptoms of anovulation. Whether treatment of subclinical hypothyroidism affects ovarian reserve indices and improves ovarian function remain a subject of further research.

Trial registration number
1072.6120.172.2022