Magnetisation transfer saturation (MTsat) shows improved tissue contrast compared with magnetisation transfer ratio (MTR), due to T1 correction, and is more sensitive to subtle myelin loss in multiple sclerosis (MS). It is not clear how MTsat performs in severely demyelinated tissue with markedly increased T1. We examine the relationship between T1app, MTsat and MTR in healthy and MS brains. We show a negative linear relationship between MTsat and T1app in white matter, which breaks down in grey matter and white matter lesions. MTsat is sensitive to modest myelin disruption, while T1app may better reflect severe damage in MS lesions.