Prehospital Emergency Pharmacology Practice Test

Thyroid hormone is a natural hormone produced by the thyroid gland and used medically as a replacement therapy when the body doesn’t make enough. The medication levothyroxine, for example, is the same molecule as the body's thyroxine and is given to treat hypothyroidism. This makes it the natural hormone among the options that’s used as a therapy.

The other substances aren’t natural hormones used for replacement: anistreplase is a thrombolytic enzyme/prodrug, not a hormone; fentanyl is a synthetic opioid analgesic; adenosine is a nucleoside involved in cellular signaling—not a hormone produced by an endocrine gland and used as a hormone replacement.