Differential Diagnosis for Lower than Normal Estrogen but Regular Periods

• Single most likely diagnosis
  • Hypothalamic amenorrhea is unlikely given regular periods, so the single most likely diagnosis is Polycystic Ovary Syndrome (PCOS) with a hormonal imbalance. PCOS can present with irregular hormone levels, including low estrogen, despite regular menstrual cycles in some cases.
• Other Likely diagnoses
  • Thyroid dysfunction: Both hypothyroidism and hyperthyroidism can affect menstrual regularity and hormone levels, including estrogen. Regular periods do not rule out thyroid issues, as some individuals may experience minimal disruption to their menstrual cycle.
  • Pituitary adenoma: A non-functioning pituitary adenoma could potentially disrupt the normal production of hormones, including estrogen, without necessarily affecting menstrual regularity.
  • Hyperprolactinemia: Elevated prolactin levels can suppress gonadotropin-releasing hormone (GnRH), leading to decreased estrogen production. Some individuals with hyperprolactinemia may still experience regular menstrual cycles.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pituitary apoplexy: Although rare, pituitary apoplexy is a medical emergency that can present with sudden headache, visual disturbances, and acute hormonal deficiencies, including a drop in estrogen levels. Regular periods before the event do not rule out this condition.
  • Craniopharyngioma: A rare type of brain tumor that can affect the pituitary gland and hypothalamus, potentially leading to hormonal imbalances, including low estrogen levels. Early detection is crucial for effective management.
• Rare diagnoses
  • Turner syndrome mosaic: Some individuals with Turner syndrome mosaicism may have a mix of normal and abnormal X chromosomes, potentially leading to variable presentations, including low estrogen levels and relatively regular menstrual cycles.
  • Resistant ovary syndrome: A rare condition characterized by ovarian resistance to gonadotropins, which can result in low estrogen levels. Menstrual cycles can be regular or irregular, depending on the severity of the resistance.
  • Autoimmune oophoritis: An autoimmune condition that targets the ovaries, potentially leading to hormonal imbalances, including low estrogen levels. The presentation can vary widely, including the possibility of regular menstrual cycles.