**Core Concept**
Catecholamine hormones, including adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine, are crucial neurotransmitters and hormones involved in the body's 'fight or flight' response. These hormones are synthesized from the amino acid tyrosine through a series of enzyme-catalyzed reactions.

**Why the Correct Answer is Right**
The synthesis of catecholamines begins in the brain, specifically in the locus coeruleus and the hypothalamus, where tyrosine is hydroxylated by the enzyme tyrosine hydroxylase to form L-DOPA. L-DOPA is then converted to dopamine by the enzyme DOPA decarboxylase. Dopamine is subsequently converted to noradrenaline by the enzyme dopamine beta-hydroxylase. Finally, noradrenaline is converted to adrenaline by the enzyme phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although the adrenal glands do play a role in the synthesis and storage of catecholamines, they are not the primary site of synthesis.
**Option B:** Incorrect because, while the adrenal glands are involved in the synthesis of adrenaline, they are not the only site of catecholamine synthesis in the body.
**Option C:** Incorrect because, although the adrenal glands do store and release catecholamines, they are not the primary site of synthesis.

**Clinical Pearl / High-Yield Fact**
The synthesis of catecholamines is tightly regulated by feedback inhibition and can be affected by various drugs, including monoamine oxidase inhibitors (MAOIs) and beta-blockers. Understanding the synthesis pathway is crucial for managing conditions such as pheochromocytoma, a rare tumor of the adrenal glands that can lead to excessive catecholamine production.

**Correct Answer: D. The adrenal medulla.**