Subclinical hypothyroidism tied to reduced ovarian reserve in later reproductive age
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Compared with their euthyroid peers, women older than 35 years who have subclinical hypothyroidism may have reduced ovarian reserve, indicated by lower antral follicle count and anti-Müllerian hormone level and higher follicle-stimulating hormone level, according to study results published in Thyroid.
“The results demonstrate that subclinical hypothyroidism was associated with a higher basal FSH concentration and a lower AMH, antral follicle count and number of aspirated oocytes following controlled ovarian stimulation,” Li Tang, MD, PhD, of the department of reproduction and genetics at First Affiliated Hospital of Kunming Medical University in China, and colleagues wrote. “Taken together, the results of this study suggest that subclinical hypothyroidism is associated with a lower ovarian reserve in older women of reproductive age.”
Tang and colleagues analyzed data from 289 women with subclinical hypothyroidism (mean age, 34.8 years) and 2,279 euthyroid women (mean age, 34.3 years) from the Reproductive Medical Center of the First Affiliated Hospital of Kunming Medical University. All participants underwent some form of treatment for infertility. The researchers assessed antral follicle count, anti-Müllerian hormone (AMH) and follicle-stimulating hormone (FSH) levels and aspirated oocytes in participants.
Among all women with subclinical hypothyroidism, mean FSH was 8.41 mIU/mL, mean AMH was 2.87 ng/mL, mean antral follicle count was 10.3 and mean number of aspirated oocytes was 8 vs. a mean FSH of 7.28 mIU/mL, a mean AMH of 3.15 ng/mL, a mean antral follicle count of 11 and a mean number of aspirated oocytes of 8.4 among all euthyroid women (P < .001 for all comparisons).
“The results of this study suggest that a thyroid function test should be included in the routine screening protocol for female fertility,” the researchers wrote. “For a patient with diminished ovarian reserve, consideration should be given to the possibility of thyroid dysfunction.”
Among women aged at least 35 years with subclinical hypothyroidism, mean FSH was 9.77 mIU/mL, mean AMH was 1.68 ng/mL, mean antral follicle count was 7.5 and mean number of aspirated oocytes was 5.1 vs. a mean FSH of 8.03 mIU/mL, a mean AMH of 2.08 ng/mL, a mean antral follicle count of 8.3 and a mean number of aspirated oocytes of 5.9 among euthyroid women aged at least 35 years (P < .001 for all comparisons).
In contrast, the researchers only found “a slightly but significantly higher FSH level” in a similar comparison with women younger than 35 years.
“It is worth noting that the age of 35 years is not a very strict cutoff. We selected this cutoff because women older than 35 years generally exhibit obvious decreases in ovarian function,” the researchers wrote. “Therefore, this study demonstrates that aging may amplify the effects of subclinical hypothyroidism on the ovarian reserve.” – by Phil Neuffer
Disclosures: The authors report no relevant financial disclosures.
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