Differential Diagnosis for 18-year-old Female with Amenorrhea
Single Most Likely Diagnosis
- Hypothalamic Amenorrhea: Given the patient's age and presentation with amenorrhea, along with relatively normal hormone levels (prolactin, FSH, LH), hypothalamic amenorrhea is a common cause of amenorrhea in young women, often related to stress, weight loss, or excessive exercise.
Other Likely Diagnoses
- Polycystic Ovary Syndrome (PCOS): Although the hormone levels provided do not strongly suggest PCOS (which typically presents with elevated LH/FSH ratio and possibly elevated androgen levels), it remains a common cause of amenorrhea in women of this age group and should be considered, especially if there are clinical signs of hyperandrogenism or ultrasound evidence of polycystic ovaries.
- Thyroid Dysfunction: Both hyperthyroidism and hypothyroidism can cause amenorrhea. Thyroid function tests (TSH, free T4) would be necessary to evaluate this possibility, as thyroid disorders are relatively common and can have significant health implications.
Do Not Miss Diagnoses
- Pituitary Tumor: Although the prolactin level is within the normal range, even a mildly elevated prolactin or a level at the upper limit of normal could be suggestive of a pituitary microadenoma, especially if other symptoms are present (e.g., galactorrhea, headache). A pituitary tumor could also cause amenorrhea through mass effect or secretion of other hormones.
- Premature Ovarian Failure (POF): Elevated FSH levels would be more indicative of POF, but it's a condition that would significantly impact fertility and should be considered, especially if the patient has other symptoms such as hot flashes.
Rare Diagnoses
- Congenital Adrenal Hyperplasia (CAH): A rare genetic disorder that can cause amenorrhea due to androgen excess. It would typically present with signs of virilization and is diagnosed through specific hormone level measurements and genetic testing.
- Androgen Insensitivity Syndrome: A rare condition where an individual with a Y chromosome has resistance to androgen hormones, leading to a female phenotype but with testes and no uterus, causing primary amenorrhea. Diagnosis involves genetic testing and physical examination.
- Gonadal Dysgenesis: Conditions such as Turner syndrome (45,X) can cause amenorrhea due to ovarian dysgenesis. These conditions often have other physical manifestations and are diagnosed through karyotyping.