Dwarfism is usually classified as proportionate, or primordial, meaning the individual is of a much smaller size than normal, while maintaining normal proportions. These individuals exhibit no physical deformity or mental impairment. As it is, no hormonal disorder has been linked to proportionate dwarfism, the cause of which is currently unknown. Slowed growth first manifests in-utero and can be detected during ultrasound scanning. The term proportionate dwarfism is sometimes wrongly attributed to other forms that also result from unknown causes, but present deformities, whereas this form does not.