A 59-year-old man was referred for Mental Health Act Assessment following several months of ‘odd behaviour’ and self-neglect reported by his neighbours. He presented as unkempt and expressed delusional ideas with respect to age, employment and identity of family members. He was fully oriented but lacked insight into his mental state and capacity for self-care. Physical examination revealed dry skin and slow relaxing reflexes. Blood investigations revealed a raised thyroid stimulating hormone and free T4 with positive thyroid peroxidise antibodies. MRI of the brain revealed frontal lobe and cerebellar atrophy, while neuropsychological assessment identified deficit in memory processing and executive functions. Despite appropriate correction of primary hypothyroidism with levothyroxine, the patient remained delusional with respect to age and employment although he showed some improvement in memory. Capacity for self-care remained poor; thus, he was eventually transferred to sheltered housing with rehabilitation.