Differential Diagnosis for Hyperprolactinemia with Low Glucose, Low Morning Cortisol and ACTH, and High Proinsulin

• Single Most Likely Diagnosis
  • Pituitary Adenoma (Prolactinoma) with Secondary Adrenal Insufficiency: This diagnosis is likely because hyperprolactinemia can be caused by a prolactinoma, which can also compress or interfere with the function of other pituitary cells, leading to secondary adrenal insufficiency (low cortisol and ACTH levels). The high proinsulin level could be indicative of beta-cell dysfunction or an insulinoma, but given the normal insulin and C-peptide levels, it might also reflect a stress response or an early sign of pancreatic dysfunction.
• Other Likely Diagnoses
  • Hypopituitarism due to Other Causes (e.g., Trauma, Infiltrative Diseases): Conditions affecting the pituitary gland can lead to hypopituitarism, which might explain the low cortisol and ACTH levels, as well as the hyperprolactinemia if the stalk effect is disrupted.
  • Insulin Resistance or Early Diabetes with Associated Hormonal Imbalance: Although insulin and C-peptide levels are normal, high proinsulin could indicate an early stage of beta-cell dysfunction. However, this would not directly explain the low cortisol and ACTH levels unless there's a broader endocrine disorder.
• Do Not Miss Diagnoses
  • Cushing's Syndrome with Cyclical Cushing's: Although less likely given the low morning cortisol, cyclical Cushing's can present with variable cortisol levels, and the high proinsulin might be seen in the context of insulin resistance associated with Cushing's.
  • Pheochromocytoma: This can cause variable blood pressure, glucose levels, and might indirectly affect pituitary function or be part of a multiple endocrine neoplasia syndrome. Missing this diagnosis could be deadly due to the potential for hypertensive crises.
• Rare Diagnoses
  • Multiple Endocrine Neoplasia (MEN) Syndromes: These syndromes can involve tumors of the pituitary, pancreas, and adrenal glands, potentially explaining the combination of hyperprolactinemia, high proinsulin, and adrenal insufficiency.
  • Lymphocytic Hypophysitis: An autoimmune inflammation of the pituitary gland that can lead to hypopituitarism, potentially explaining the hormonal imbalances, though it's a rare condition.
  • Familial Cushing's Syndrome due to Primary Pigmented Nodular Adrenocortical Disease (PPNAD): Part of the Carney complex, which can also include pituitary tumors, explaining the hyperprolactinemia and potentially the other hormonal abnormalities.