Differential Diagnosis for Amenorrhea in a 19-Year-Old Woman
- Single Most Likely Diagnosis
- Functional Hypothalamic Amenorrhea (FHA): This condition is the most likely diagnosis given the patient's recent increase in physical activity (collegiate-level soccer, exercising twice daily) and potential psychological stress (first semester of college, taking extra classes). These factors can disrupt the hypothalamic-pituitary-gonadal axis, leading to amenorrhea. The patient's normal prolactin and TSH levels, absence of weight loss, and lack of menstrual bleeding after a progesterone challenge support this diagnosis.
- Other Likely Diagnoses
- Polycystic Ovary Syndrome (PCOS): Although the patient's menstrual cycles were previously regular, PCOS can present at any time, especially with changes in lifestyle or weight. However, the absence of other typical PCOS symptoms (such as hirsutism, acne, or obesity) and the normal response to the progesterone challenge make this less likely.
- Premature Ovarian Insufficiency (POI): This condition involves the loss of ovarian function before the age of 40. While it's less common in a 19-year-old, it could be considered, especially if there's a family history or other symptoms. However, the patient's recent onset of amenorrhea and lifestyle changes point more towards FHA.
- Do Not Miss Diagnoses
- Pituitary Tumor: Although prolactin levels are normal, a pituitary tumor (especially a microadenoma) could still be present and cause amenorrhea. The lack of visual changes or other symptoms makes this less likely, but it's crucial to consider due to the potential severity of pituitary tumors.
- Thyroid Dysfunction: Despite normal TSH levels, thyroid dysfunction (particularly hypothyroidism) can sometimes present with amenorrhea. It's essential to ensure that thyroid function is thoroughly evaluated.
- Rare Diagnoses
- Congenital Adrenal Hyperplasia: This is a group of inherited disorders that affect the adrenal glands, potentially leading to amenorrhea among other symptoms. It's rare and typically presents with other signs such as virilization or Cushingoid features.
- Androgen Insensitivity Syndrome: A rare condition where an individual is genetically male (XY) but has resistance to male hormones (androgens), leading to the development of female external genitalia but with undescended testes and no uterus. This would be an extremely rare cause of primary amenorrhea but is less likely given the patient's reported menarche and subsequent secondary amenorrhea.