exhibiting excessive tone or tension

Pronunciation:
hi-pur-TAHN-ick

In a sentence:
Carrie’s hypertonic bladder was the talk of the town; especially during the winter months, when people would gather from far and wide to watch her lose control and shiver with shame as she performed single and double axels on the skating rink.

In a different sentence:
Harry’s hypertonic muscles were impressive to some, but seemed excessive to most.