Congenital Adrenal Hyperplasia leads to the virilization of the foetus. It occurs due to an enzyme deficiency in the corticosteroid production pathway i.e. 21-hydroxylase which converts progesterone to deoxycorticosterone. The reduced levels of corticosteroids results in the negative feedback loop that leads to adrenal hyperplasia.

It is less common for a girl of this age to develop fibroids, endometriosis and endometrial polyps, although these are all causes of severe dysmenorrhea. Chronic pelvic infection can be due to sexually transmitted disease but the history does not mention any previous episodes of pelvic pain or symptoms of infection such as fever. In this case, it is most likely that she has primary dysmenorrhea. Primary dysmenorrhea, in which no pathological cause can be identified, is believed to be due to the prostaglandins released by the secretory endometrium. If secondary dysmenorrhea is suspected, then endometriosis would be the most prominent cause.

While hysteroscopic and laparoscopic examinations are commonly done in adult women to rule out organic causes such as those mentioned earlier, in younger girls, they are usually only carried out if pain management with, for example, NSAIDs and the use of COCPs, have failed to either provide symptom relief or reduction.

FEV1 and FVC are unchanged. FEV1/FVC ratio remains the same in pregnancy

The vaginal epithelium is made of squamous cells. Hence the most common carcinoma that occurs in the Vagina is squamous cell carcinoma. Diagnosis is made with vaginal biopsy. Usually the pain only presents if the disease extends beyond the vagina involving the perineal nerves.

Squamous cell carcinoma is the most common type of vaginal cancer.

When the palpated uterine size is in discrepancy with the expected size based on the duration of amenorrhoea, it can have several causes including reduced fluid volume or fetal growth (both of which are more common when there is fetal malformation), or miscalculated age of gestation as a result of wrong dates or actual ovulation occurring at a later date than expected. Reduced fluid volume and fetal growth are the most likely aetiologies during the third trimester of pregnancy, unlike in this patient at 20 weeks age of gestation.

Premature rupture of membranes is less likely the cause when there is negative vaginal fluid loss like this patient.

The most likely cause in this case is that ovulation did not occur as expected, especially when the patient ceased her OCPs during this period. In some instances, ovulation can occur 2 weeks later in about 50% of women, 6 weeks later in 90%, and may still not occur 12 months later in 1% of women.

The other listed statements are unlikely to explain the discrepancies in dates and the observed uterine size in this patient.

During pelvimetry, the shape of the pubic arch is usually examined. It helps in determining the outcome of the type of fetal delivery.

An ovarian cyst is a sac filled with liquid or semiliquid material that arises in an ovary. Although the discovery of an ovarian cyst causes considerable anxiety in women owing to fears of malignancy, the vast majority of these lesions are benign. Most patients with ovarian cysts are asymptomatic, with the cysts being discovered incidentally during ultrasonography or routine pelvic examination. Some cysts, however, may be associated with a range of symptoms, sometimes severe, including the following:

Pain or discomfort in the lower abdomen

Severe pain from torsion (twisting) or rupture – Cyst rupture is characterized by sudden, sharp, unilateral pelvic pain; this can be associated with trauma, exercise, or coitus. Cyst rupture can lead to peritoneal signs, abdominal distention, and bleeding (which is usually self-limited)
Discomfort with intercourse, particularly deep penetration
Changes in bowel movements such as constipation
Pelvic pressure causing tenesmus or urinary frequency
Menstrual irregularities
Precocious puberty and early menarche in young children
Abdominal fullness and bloating
Indigestion, heartburn, or early satiety
Endometriomas – These are associated with endometriosis, which causes a classic triad of painful and heavy periods and dyspareunia
Tachycardia and hypotension – These may result from haemorrhage caused by cyst rupture
Hyperpyrexia – This may result from some complications of ovarian cysts, such as ovarian torsion
Adnexal or cervical motion tenderness

Underlying malignancy may be associated with early satiety, weight loss
achexia, lymphadenopathy, or shortness of breath related to ascites or pleural effusion

The absence of fever or vaginal discharge rules out PID

The absence of pain on the right lower quadrant, fever, nausea and vomiting rule out appendicitis.

The patient has regular menses, no vaginal bleeding no signs of shock that rules out ectopic pregnancy.

her symptoms are also not consistent with the presentation of leiomyoma. Leiomyoma presents with enlarged uterus, pelvic pressure. It early causes pain when it is complicated with red degeneration which usually occurs in pregnancy.

After ovulation, the dominant follicle turns into a corpus luteum and begins to secrete progesterone. To confirm ovulation, serum progesterone or its metabolite in urine, can be measured. A single serum progesterone level >3 ng/ml in mid‐luteal phase has been used to retrospectively detect ovulation.

Tamoxifen and Raloxifene are drugs which acts as selective estrogen receptor modulators.
Their mechanisms of action are competitive inhibitor of estrogen binding and mixed agonist/antagonist action respectively.
Commonly indicated in prevention of breast cancer in high-risk patients. Tamoxifen as adjuvant treatment of breast cancer and Raloxifene in postmenopausal osteoporosis.
Adverse effects include:
– Hot flashes
– Venous thromboembolism
– Endometrial hyperplasia & carcinoma (tamoxifen only)
– Uterine sarcoma (tamoxifen only)
Adjuvant endocrine therapy is commonly used option for treatment of nonmetastatic, hormone-receptor-positive breast cancer; and the most commonly used endocrine agents include tamoxifen, aromatase inhibitors, and ovarian suppression via GnRH agonists or surgery.

Tamoxifen is a selective estrogen receptor modulator which is an estrogen receptor antagonist in the breast.  It is the most preferred adjuvant treatment for pre-menopausal women at low risk of breast cancer recurrence.  Tamoxifen is also a second-line endocrine adjuvant agent for postmenopausal women who cannot use aromatase inhibitor therapy due to intolerable side effects.
Tamoxifen acts as an estrogen agonist in the uterus and stimulates excessive proliferation of endometrium. Therefore, tamoxifen use is associated with endometrial polyps in premenopausal women, and endometrial hyperplasia and cancer in postmenopausal women. These effects will continue throughout the duration of therapy and resolves once the treatment is discontinued. Even with all these possible complications, benefits of tamoxifen to improve the survival from breast cancer outweighs the risk of endometrial cancer.

In postmenopausal women, tamoxifen has some estrogen-like activity on the bone, which can increase bone mineral density and thereby reduce the incidence of osteoporosis significantly.  However, tamoxifen is generally not a first-line agent for osteoporosis in treatment due to the marked risk of endometrial cancer.

Dysplasia of the cervical transformation zone is typically caused due to chronic infection by human papillomavirus, and tamoxifen has no known effects on the cervix.

Tamoxifen is not associated with any increased risk for adenomyosis, which is characterised by ectopic endometrial tissue in the myometrium.

Intimal thickening of the coronary arteries is a precursor lesion for atherosclerosis. Tamoxifen helps to decrease blood cholesterol level and thereby protect against coronary artery disease.

Tamoxifen is an estrogen antagonist on breast tissue and is used in the treatment and prevention of breast cancer, but it also acts as an estrogen agonist in the uterus and increases the risk of development of endometrial polyps, hyperplasia, and cancer.