Are.thyroid issues life threatening like cancers?

Thyroid: There are a number of thyroid problems, some of which are cancer. When the thyroid is either overactive or hypoactive it can cause significant problems which can become life-threatening.

Usually not: Most thyroid conditions are not life threatening, however there are exceptions. As you indicated, some types of thyroid cancer can be life threatening. A non cancerous condition that can be life threatening is thyroid storm, an enormous release of thyroid hormone in a small number of patients with an over active thyroid. It can result in agitation, fever, fast pulse, heart failure, and death.

Can be: Thyroid disorders are life threatening if there is extreme hyperactivity such as thyroid storm (thyrotoxicosis). This is a rare but life threatening form of hyperthyroidism resulting in fever, dehydration, heart palpitations or even coma. More commonly, hypothyroid (low thyroid) or hyperthyroid (over active thyroid) can have significant side effects but are not immediately life threatening.