When people have an overactive thyroid, a drug called propranolol lowers a bone breakdown marker in their urine — but it doesn’t do this by changing levels of a key thyroid hormone.

If someone has an overactive thyroid, taking propranolol might lower a certain waste product in their urine, and this probably happens because of how the drug affects cell walls, not because of its usual heart-slowing effects or changes to thyroid hormones.

A heart medication called propranolol might help slow down bone breakdown in people with an overactive thyroid, based on changes in a specific substance found in their urine.

If someone has an overactive thyroid, taking the heart medication propranolol might help lower certain thyroid hormone levels in their blood — possibly because the drug affects how the body converts one hormone into another.

If someone has an overactive thyroid, taking the heart medication propranolol might lower certain thyroid hormone levels, and how much it blocks the body’s ‘fight-or-flight’ system could be linked to how strong this effect is.

Even in people with healthy thyroids, taking the heart medication propranolol might change how their body processes thyroid hormones — raising some levels, lowering others.