PRL and hypothyroidism: Some experts believe have observed decreased clearance of androstendione and estrone and an increase in aromatization that lead to high free estrogen levels, increased thyrotropin-releasing hormone (TRH) levels that lead to increased prolactin (PRL) levels, changes in the gonadotropin-releasing hormone (GnRH) pulse that cause luteinizing hormone (LH) peak delays and luteum function disorders, and coagulation defects in individuals with hypothyroidism; all of these changes eventually cause ovulation and fertility problems [27, 37].