Primary polydipsia (PP) is etiologically associated with physical factors and psychiatric disorders ("psychogenic polydipsia"). We present the case of a 28-year-old man with severe symptoms of polydipsia and polyuria. After a comprehensive physical assessment, the only finding was a lesion suggestive of pituitary microadenoma in the magnetic resonance imaging (MRI) scan of the brain. A thorough clinical and diagnostic assessment and the administration of a wide range of psychometric tools revealed no major psychiatric disorder apart from chronic anxiety and mild depressive symptoms. Our patient's PP symptoms might be associated with a dysfunction of the thirst center, which is located closely to the neuroanatomical lesion found in the MRI scan. Given that the underlying pathophysiology of PP remains, to a large extent, unclear, we emphasize on the difficulties to distinguish between PP's subtypes.