**Question:** All of the following statements regarding benefits of combined oral contraceptive pills are TRUE, EXCEPT:

A. Reduces the risk of endometrial and ovarian cancer
B. Increases the risk of venous thromboembolism
C. Can cause weight gain
D. Improves mood and reduces premenstrual syndrome symptoms

**Core Concept:** Combined oral contraceptive pills (OCPs) are a type of hormonal contraceptive containing estrogen and progestin. They have several benefits, including reducing the risk of endometrial and ovarian cancer, improving mood, and reducing premenstrual syndrome (PMS) symptoms. However, they do increase the risk of venous thromboembolism (VTE), which is a type of blood clot that may lead to serious complications.

**Why the Correct Answer is Right:** Option C, stating that OCPs cause weight gain, is incorrect. Combined OCPs primarily work by suppressing the hypothalamic-pituitary-ovarian axis, which results in a decrease in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This, in turn, leads to a decrease in sex hormone-binding globulin (SHBG) production, freeing up more free testosterone in women, which may contribute to weight gain.

**Why Each Wrong Option is Incorrect:**

A. Reduced risk of endometrial and ovarian cancer: Combined OCPs have been shown to reduce the risk of these cancers due to their anti-estrogenic and anti-androgenic effects, respectively.

B. Increased risk of venous thromboembolism (VTE): The correct answer explains that OCPs increase the risk of VTE due to the combined estrogen and progestin components that affect blood coagulation factors and increase blood viscosity. This increases the risk of blood clot formation, particularly in women with a history of VTE or other risk factors.

D. Improved mood and reduced premenstrual syndrome (PMS) symptoms: Combined OCPs suppress the hypothalamic-pituitary-ovarian axis, thereby reducing the symptoms of PMS and improving mood due to reduced prostaglandin production and decreased LH and FSH levels.

**Clinical Pearls:**

1. Understanding the pharmacology and mechanism of action of OCPs helps to predict potential side effects and benefits accurately.
2. Assessing the patient's medical history, specifically risk factors for VTE, is essential when prescribing OCPs to minimize adverse effects.
3. Recognizing the impact of OCPs on mood and PMS symptoms can help in counseling patients regarding potential benefits and side effects.