HomeArticlesGraves’ Disease – Hyperthyroidism – Everything You Need to Know – MADE EASY
Graves’ Disease – Hyperthyroidism – Everything You Need to Know – MADE EASY
December 26, 2019
Hey guys. Today we’re going to talk about Grave’s disease. which is a form of hyperthyroidism. But before we get into that, I think it’s important to briefly explain how the thyroid hormones are made maintained and how they effect our body. So, what happens is that the hypothalamus releases these hormones called; the ‘thyrotropin releasing hormone’ or TRH which act on the anterior pituitary and causing it to release these other hormones called the ‘thyroid stimulating hormones’ or TSH which I’m drawing here as triangles. The TSH will then bind to its receptors on the thyroid gland regulating thyroid hormone production by the follicular cells of the thyroid gland. T4 and T3 are the two forms of thyroid hormones T3 being the more active form and it is made in less quantity than T4 but T4 can get converted into T3 in the target tissues, which is important to know since there is a medication, which we will talk about that inhibits this conversion. Now, once we have enough thyroid hormones meaning that there is a normal level of thyroid hormones in our body there will be a negative feedback on the hypothalamus. This will lead to inhibition of the release of TRH which then leads to inhibition of the release of TSH and therefore, decrease production of thyroid hormones. The thyroid hormones can pretty much affect our entire body They can help with bone growth neurons and CNS maturation, they can work on the heart by stimulating the Beta-1 receptors effecting the cardiac output, the heart rate, stroke volume and contractility. They can effect the respiratory rate, body temperature, and basal metabolic rate. They can also lead to glycogenolysis lipolysis and gluconeogenesis. Now in case of Grave’s disease, which is an autoimmune, type 2 hypersensitivity reaction The body forms these antibodies called the ‘thyroid stimulating immunoglobulins’ which mimic the ‘thyroid stimulating hormones’ and bind to their receptors and activate the secretion of T4 and T3. Now, we’re still going to have the negative feedback on the hypothalamus. leading to inhibition of the release of TRH and TSH. This is very important to know because the levels of TSH are one of the main diagnostic tests that we measure in patients suspected of any form of hyperthyroidism including Grave’s disease. The reason that we don’t measure the TRH levels is due to the fact that it also causes the anterior pituitary to release other hormones such as ‘prolactin’. Therefore it is not very diagnostic. So, everything that we talked about as far as the effects of thyroid hormone goes in our body will increase in case of Grave’s disease leading to many different signs and symptoms throughout the body, which includes; bone loss, psychosis, mania, agitation, insomnia, tremor, excessive sweating, heat intolerance, weight loss despite increase in appetite, diarrhea, fine hair and hair loss, palpitation, arrhythmias such as atrial fibrillation, and muscle weakness due to inflammation of different muscles. We can also see exophthalmus or proptosis which is the bulging out of the eyes due to inflammation of the eye muscles which can present either as unilateral or bilateral. We can also see goiter which is the enlargement of the thyroid gland as well as ‘pretibial myxedema’ which is a waxy, discolored induration of the skin due to inflammation. Which has an incidence rate of about, 1 to 5% in patient’s with Grave’s disease. Now, what do we see in the lab findings? Well, we’re obviously going to see an increase in thyroid hormones as well as a decrease in TSH levels. But, what’s really important is the diffuse increase in the radioactive iodine uptake as shown in the picture which allows us to differentiate Grave’s disease from other forms of hyperthyroidism. The other causes of hyperthyroidism includes; Subacute thyroiditis, which tends to be painful Silent thyroiditis, which tends to be painless Thyroid adenoma also known as toxic adenoma which is a benign tumor of the thyroid gland Exogenous thyroid hormones, which can be seen in some individuals, who are trying to lose weight but end up taking too much thyroid hormones. as well as pituitary adenoma, which is a tumor of the pituitary gland. Now, when we compare all these together we can see that they all present with ‘low’ TSH levels except for pituitary adenoma which actually increases the release of TSH and therefore increases the thyroid hormone production. But like I just mentioned the only thing that is different is the diffuse increase in radioactive iodine uptake in Grave’s disease compared to the others. We don’t use this test in pituitary adenoma, since the problem is not due to the thyroid gland. Instead we can use MRI in patients who are suspected of having pituitary adenoma. So there are different ways for treating Grave’s disease. One way is, ‘propranolol’, which is a Beta-blocker that inhibits the conversion of T4 to its more active form, which is T3. It can also be used to treat tachycardia. Another way to treat Grave’s disease, is by using PTU or Methimazole which both inhibit the production of thyroid hormones. Whats important to know, is that PTU can also be used in pregnancy. One of the biggest side effect of these two drugs is agranulocytosis, which causes the reduction of WBCs and makes the patient more prone to infections as well as the opportunistic infections So you have to make sure to check the patient’s WBC count every few weeks. and stop the medication if you see a decrease in WBC levels. We can also use Radioiodine, which is the most cost effective and the best longterm management as well as the permanent cure for Grave’s disease The major side effect of radioiodine is, hypothyroidism, since it destroys the entire thyroid gland. Surgery is rarely done, unless the large goiter compresses the trachea preventing the patient from breathing. Or, if there is a suspicious nodule, or the patient is suspected of having cancer. Some of the side effects of the surgery includes; damage to the recurrent laryngeal nerve which controls the voice box, and can lead to hoarseness or voice loss. And hypoparathyroidism since the parathyroid glands are located on the posterior aspect of the thyroid gland. Therefore removing them can lead to hypocalcemia. To treat the eye manifestation of the Grave’s disease, we can use lubricant eye drops or NSAID eye drops in the mild form of the disease and if the manifestations are very severe, we can use steroids or do orbital decompression.