Kocher's sign is a

medical sign Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

that denotes an eyelid phenomenon in

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

and Basedow's disease. In fixation on a fast upwards movement there occurs a convulsive retraction of the eyelid.

References

Endocrinology {{Med-sign-stub