All amino acid derived hormones bind cell membrane receptors except one lipid-soluble group. Which group is the exception?
APeptide hormones
BProtein hormones
CThyroid hormones
DCatecholamines
Answer & Solution
Correct answer: C. Thyroid hormones
1. A receptor sits inside the cell only for hormones that can cross the lipid bilayer.
2. Steroids cross easily because cholesterol is their parent molecule.
3. Thyroid hormones carry benzene rings studded with iodine, which makes them lipid soluble as well.
4. So thyroid hormones enter the cell and reach receptors that are already bound to DNA.
5. Peptide and protein hormones are hydrophilic and must signal from the cell surface through a second messenger.
6. Catecholamines are also water soluble, so they too stay at the membrane and never reach a nuclear receptor.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.2 Hormones_
Keep practising The Endocrine System
Browse all The Endocrine System questions for DHA Medical Licensing Exam, or explore more Physiology topics.
Related questions
Pick the bigger endocrine numberBuild thyroid hormone in orderMerge hormones into their classSort the pituitary hormonesFill the endocrine bingo cardFrom which embryonic tissue does the anterior pituitary gland arise?The kidneys release erythropoietin in response to what?Which cells take up glucose without needing insulin at all?