What laboratory findings are most likely present in a 34-year-old woman with secondary amenorrhea (absence of menstruation), a history of non-Hodgkin lymphoma treated with chemotherapy, and physical examination findings of dry vaginal mucosa and a small uterus, with a negative pregnancy test and normal blood pressure (normotension) and pulse rate (normocardia)?

Differential Diagnosis for Amenorrhea

The patient presents with 3 months of amenorrhea, a history of irregular periods, and a history of non-Hodgkin lymphoma treated with chemotherapy. The following differential diagnoses are considered:

• Single Most Likely Diagnosis
  • Premature Ovarian Insufficiency (POI): Given the patient's history of chemotherapy, which is a known risk factor for POI, and her symptoms of amenorrhea and dry vaginal mucosa, this diagnosis is highly likely. Chemotherapy can damage the ovaries, leading to premature menopause.
• Other Likely Diagnoses
  • Hypothalamic Amenorrhea: The patient's BMI is 28 kg/m2, which is considered overweight. This, combined with the potential for stress from her medical history, could contribute to hypothalamic amenorrhea. However, the absence of fatigue and the patient's normal physical examination make this less likely than POI.
  • Pituitary Dysfunction: Although the patient denies symptoms such as headaches or galactorrhea, pituitary dysfunction (e.g., due to a non-functioning pituitary adenoma) could still be a consideration. However, the lack of specific symptoms and a normal physical examination make this less likely.
• Do Not Miss Diagnoses
  • Pituitary Apoplexy: Although rare and less likely given the patient's lack of specific symptoms like sudden, severe headache, this condition is potentially life-threatening and should not be missed. Pituitary apoplexy is a medical emergency that requires immediate attention.
  • Craniopharyngioma or Other Brain Tumors: These could affect the hypothalamic-pituitary axis, leading to amenorrhea. While the patient does not have symptoms like headaches or visual changes, these conditions are serious and should be considered to avoid missing a potentially deadly diagnosis.
• Rare Diagnoses
  • Asherman Syndrome: This condition, characterized by intrauterine adhesions, can lead to amenorrhea. However, it is less common and typically associated with a history of uterine surgery or infection, which is not mentioned in the patient's history.
  • Resistant Ovary Syndrome: A rare condition where the ovaries do not respond to gonadotropins, leading to amenorrhea. This diagnosis would be considered if other more common causes are ruled out.