Okay, let's tackle this question. The patient has episodic hypertension, headache, and a thyroid nodule. The question is asking for the investigation of choice. Hmm.

First, I need to think about the possible differentials. Episodic hypertension and headaches could be signs of a pheochromocytoma. That's a tumor of the adrenal medulla that secretes catecholamines. But there's also a thyroid nodule mentioned. Wait, some pheochromocytomas are part of syndromes like Multiple Endocrine Neoplasia (MEN) types 2A and 2B, which also involve medullary thyroid carcinoma. So the thyroid nodule here might be related to that.

The investigation of choice for pheochromocytoma is measuring plasma free metanephrines or 24-hour urine metanephrines. These are the metabolites of catecholamines and are more specific than plasma catecholamines. If the tests are positive, imaging like MRI or CT of the adrenal glands would follow. But since there's a thyroid nodule, maybe they also need to check for medullary thyroid carcinoma. Calcitonin levels or a thyroid ultrasound could be part of that. However, the question is about the primary investigation for the episodic symptoms.

Looking at the options, the correct answer would be plasma free metanephrines. The other options might be things like TSH, cortisol, or something else. Let me think about the wrong options. If an option is TSH, that's for hypothyroidism or hyperthyroidism, not pheochromocytoma. Cortisol would be for Cushing's syndrome. Thyroid function tests might be part of the workup for the nodule but not the main issue here. So the key is linking the episodic hypertension to pheochromocytoma and the thyroid nodule to MEN 2B. The investigation of choice is plasma free metanephrines.

**Core Concept**
This question tests the diagnostic approach to episodic hypertension and a thyroid nodule, which are classic features of **pheochromocytoma** and **medullary thyroid carcinoma (MTC)** in **Multiple Endocrine Neoplasia type 2B (MEN 2B)**. The investigation must target **catecholamine excess** and **thyroid pathology**.

**Why the Correct Answer is Right**
The combination of episodic hypertension, headaches, and a thyroid nodule strongly suggests **pheochromocytoma** (adrenal medulla tumor) and **MTC**. The **investigation of choice for pheochromocytoma** is **plasma free metanephrines**, which are **highly sensitive and specific** for detecting catecholamine-secreting tumors. Elevated metanephrines confirm the diagnosis, while **calcitonin testing** or **thyroid ultrasound** would assess the thyroid nodule for MTC. This dual approach addresses both adrenal and thyroid pathologies in MEN 2B.

**Why Each Wrong Option is Incorrect**
**Option A:** *Plasma catecholamines* are less sensitive than metanephrines and can be falsely normal in episodic cases.
**Option B:** *24-hour urinary cortisol* is

✓ Correct Answer: B. Urinary catecholomine and aspiration of nodule