**Core Concept**
Intracellular receptors are a type of receptor found within cells that play a crucial role in the regulation of gene expression in response to various signals, including hormones and other signaling molecules. These receptors are localized in the cytoplasm or nucleus and can modulate gene transcription upon ligand binding.

**Why the Correct Answer is Right**
Intracellular receptors are responsible for mediating the effects of steroid hormones, thyroid hormones, and certain vitamins. Upon ligand binding, these receptors undergo conformational changes that allow them to translocate to the nucleus, where they interact with specific DNA sequences to regulate gene transcription. This process is critical for the regulation of various physiological processes, including metabolism, growth, and development.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because intracellular receptors are not primarily involved in the regulation of ion channels or synaptic transmission.
**Option B:** This option is incorrect because G-protein coupled receptors (GPCRs) are a type of transmembrane receptor, not intracellular receptors.
**Option C:** This option is incorrect because nuclear receptors are a subfamily of intracellular receptors that regulate gene transcription, but there are other types of intracellular receptors as well.

**Clinical Pearl / High-Yield Fact**
Intracellular receptors play a critical role in the regulation of gene expression in response to various signals, including hormones and other signaling molecules. Understanding the mechanisms of intracellular receptor signaling is essential for the diagnosis and treatment of various endocrine disorders.

**Correct Answer:** C.