**8.5 Thyroid gland disorders**

It is well known that hypothyroidism without therapy increases the risk of abortion. Treatment before attempting a pregnancy is clearly recommend as well as keeping a TSH level between 1.0–2.5 UIU/ml in the first trimester. In cases with TSH levels higher than 2.5 MIU/ml, levothyroxine should be started at a minimum dose of 50 μg/d.

Anti-thyroid Abs is associated with RPLs when detected before the start of pregnancy or at an early stage.

Hypothyroidism is involved with obstetric complications like infertility, abortions, anemia, preeclampsia, placental abruption, fetal death, preterm birth, and low birth weight [55–58].

### **8.6 Alloimmune dysfunction**


#### **8.7 Diminished ovarian reserve**

Increased levels of FSH in the early follicular phase of menstrual cycle are significant for diminished ovarian reserve. In the least years, another marker antimüllerian hormone is better to identify the number of follicular units for recruitment. It is recommended that women with RPL visit healthcare services to have appropriate counselling to treat endocrinological disorders [59].

### **8.8 PCOS**

Polycystic ovary syndrome (PCOS) is associated with increased frequency of RPL and has an uncertain prevalence, because factors associated with PCOS such as obesity, insulin resistance, LH rise, and hyperandrogenemia may be the reason and not PCOS as a whole [60–68]. The incidence of abortions in spontaneous ovulation is difficult to determine. Diagnostic criteria for this heterogeneous disorder have not been present in the past. Hypersecretion of LH and elevate androgen levels possibly led to RPL [60–68]. The association of excess androgens and RPL is not clear. The hyperinsulinemia in PCOS that is a consequence of insulin resistance involving plasminogen activator inhibitor-1(PAI-1) which inhibits plasminogen activation and subsequent fibrinolysis, has potential thromboembolic effect that makes women with PCOS in high risk for recurrent pregnancy loss [60–68].
