**Question:** All of the following are true regarding Grave's disease except: March 2008

A. Thyroid hormone excess causes diastolic hypertension
B. Thyroid hormone excess stimulates diastolic hypertension
C. Thyroid hormone excess causes symptoms of thyrotoxicosis
D. Thyroid hormone excess causes symptoms of hypothyroidism

**Correct Answer: D. Thyroid hormone excess causes symptoms of hypothyroidism**

**Core Concept:**
Grave's disease is a common cause of hyperthyroidism, which is characterized by overproduction of thyroid hormones (thyroxine and triiodothyronine) by the thyroid gland. Hyperthyroidism can lead to a wide range of clinical symptoms and signs, collectively known as thyrotoxicosis.

**Why the Correct Answer is Right:**
Hyperthyroidism in Grave's disease primarily affects the cardiovascular system, leading to tachycardia, hypertension, and autonomic symptoms. The correct answer, D, states that thyroid hormone excess causes symptoms of hypothyroidism, which is incorrect for Grave's disease. Hypothyroidism is characterized by low thyroid hormone levels and presents with symptoms like fatigue, weight gain, cold intolerance, and constipation, none of which are seen in Grave's disease.

**Why Each Wrong Option is Incorrect:**
A. Thyroid hormone excess does not cause diastolic hypertension; instead, it causes tachycardia and autonomic symptoms. Diastolic hypertension is a feature of hypothyroidism, which is inconsistent with the scenario in Grave's disease.
B. Thyroid hormone excess actually stimulates the heart rate (tachycardia) rather than causing diastolic hypertension. Diastolic hypertension is not a common feature of Grave's disease.
C. Thyroid hormone excess leads to symptoms and signs of thyrotoxicosis, which is consistent with the condition. In Grave's disease, the thyroid gland produces excessive thyroid hormones, leading to thyrotoxicosis.
D. As mentioned, thyroid hormone excess causes symptoms of hypothyroidism but not diastolic hypertension. Diastolic hypertension is a feature of hypothyroidism, which is inconsistent with the scenario in Grave's disease.

**Clinical Pearl:**
Grave's disease is a common cause of hyperthyroidism, often presenting with symptoms of thyrotoxicosis, such as tachycardia, weight loss, anxiety, and tremors. The thyroid gland in Grave's disease produces excessive thyroid hormones, leading to the manifestation of thyrotoxicosis. Diastolic hypertension, on the other hand, is a feature of hypothyroidism, which is not the case in Grave's disease.