Hyperthyroidism resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Pervaiz Laghari, MD[2]

Overview

Hyperthyroidism and thyroid storm are disease states that result from thyroid hormone-induced hypermetabolism. The excess thyroid hormone is released from the thyroid gland as a result of excess thyroid hormone production, or by processes that disrupt the follicular structure of the gland with subsequent release of stored hormone . Most patients with severe hyperthyroidism present with a dramatic symptom constellation. Hyperthyroidism's typical symptoms include palpitations,heat intolerance, increased bowel movement frequency tremor, anxiety, weight loss despite normal or increased appetite and shortness of breath.Goiter is commonly found on physical examination.

Specific organ systems

Cardiovascular	Heart rate is increased,Systolic hypertension ,pulse pressure is widened, congestive heart failure, Atrial fibrillation
Neuropsychiatric	Anxiety, tremor, restlessness, irritability,insomnia,psychosis, agitation,depression, seizures
Respiratory	Dyspnea, tracheal obstruction, exacerbate underlying asthma,Pulmonary arterial systolic pressure is increased
Gastrointestinal	Weight loss,hyperphagia,hyperdefecation and malabsorption
Skin	Sweating,Onycholysis,Hyperpigmentation,Thinning of the hair
Eyes	Stare and lid lag, ophthalmopathy.
Genitourinary	Urinary frequency and nocturia
Hematologic	Normochromic, normocytic anemia
Neck	Thymic enlargement
Bone	Osteoporosis and an increased fracture risk

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Thyroid storm

Common Causes

• Graves disease
• Painless or transient (silent) thyroiditis
• Toxic adenoma (Plummer disease)
• Toxic multinodular goiter
• Postpartum thyroiditis
• Hyeremesis gravidarum
• Subacute granulomatous (de Quervain) thyroiditis
• Drug-induced thyroiditis

Diagnosis

Shown below is an algorithm summarizing the diagnosis of hyprthyroidism according to the American Thyroid Association guidelines. Serum TSH measurement has the highest sensitivity and specificity of any single blood test used in the evaluation of suspected thyrotoxicosis and should be used as an ini-tial screening test . However, when thyrotoxicosis is strongly suspected, diagnostic accuracy improves when aserum TSH, free T4, and total T3 are assessed at the initial evaluation. Serum TSH levels are considerably more sensitive than direct thyroid hormone measurements for assessing thyroid hormone excess. In overt hyperthyroidism, serum free T4,T3,or both are elevated, and serum TSH is subnormal (usually<0.01mU/L ina third-generation assay). In mild hyperthyroidism, serum T4 and free T4 can be normal, only serum T3 may be elevated, and serum TSH will be low or undetectable. The diagnosis of a thyrotoxic crisis is made entirely on the clinical findings. Most importantly, there is no difference in thyroid hormone levels between patients with "uncomplicated" thyrotoxicosis and those undergoing a thyroid storm.

Clinical assessment of signs & symptoms for hyperthyroidism: Tachycardia Palpitations Anxiety, insomnia Fine tremors in outstretched hands Heat intolerance Diaphoresis Weight loss irregular pulse (in atrial fibrillation) dyspnea orthopnea brisk deep tendon reflexes proximal muscle weakness pretibial myxedema (Graves’ disease) lid lag, lid retraction, decrease lacrimation (thyroid eye disease)

Measure serum Thyroid stimulating hormone levels

Low TSH

High TSH

Mild hyperthyroidism: Serum T4 and T3 values in normal range or only T3 levels are elevated.

Overt hyperthyroidism: Both serum T3 and T4 levels elevated

Elevated serum T4 and T 3 levels

Perform thorough physical examination of thyroid gland and look for signs for thyroid eye disease. Thyroid gland diffusely enlarged with symmetrical hypertrophy and new onset of ocular symptoms

Repeat TSH levels in serial dilution

Yes. Graves' disease

No

Positive

Negative

Measure serum assays of TRAb and radioactive iodine uptake thyroid scan

High TSH levels due to hetrophilic antibodies

Look out for pituitary lesion

Measurement of serum levels of human anti-mouse antibodies

* Perform MRI Brain High ratio of the serum level of alpha subunit of the pituitary glycoprotein hormone

Diffuse increase in iodine uptake

Localized increase in iodine uptake

Subnormal or absent uptake of iodine

Graves' disease

Toxic nodular goiter

Subacute thyroiditis/ Postpartum thyroiditis

Factitious ingestion of thyroid hormones

Excess intake of iodine recently

High levels of thyroglobulin in serum

Low thyroglobulin levels

Measure spot urine iodine or 24 hour urine iodine level

Treatment

Shown below is an algorithm summarizing the treatment of Graves' disease according to the American Thyroid Association guidelines.

Overt Graves' disease

Antithyroid medications

Radioactive iodine ablation

Surgery

Methimazole (MMI) is a drug of choice because of its lower side effects profile. It should be continued for a minimum duration of 12 to 18 months. Regular monitoring with TSH and TRAb should be done.

Total or near-total thyroidectomy is recommended. The advantages are: High cure rate Zero recurrence rate with total thyroidectomy.

Drug List

Drug	Initial daily dose	Mechanisim of action
Beta blocker	Propranolol 60 to 80 mg orally every four to six hours,	Control the symptoms and signs
Thionamide	PTU 200 mg every four hours or methimazole,20 mg orally every four to six hours	Block new hormone synthesis
Iodine	(Lugol's) solution, 10 drops (6.25 mg iodide/iodine per drop [0.05 mL]) three times daily	Block the release of thyroid hormone
Glucocorticoids	Hydrocortisone, 100 mg intravenously every eight hours	Reduce T4-to-T3 conversion, promote vasomotor stability, possibly reduce the autoimmune process in Graves' disease, and possibly treat an associated relative adrenal insufficiency
An iodinated radiocontrast agent	0.5 to 1 g once daily.	inhibit the peripheral conversion of T4 to T3
Bile acid sequestrants	Cholestyramine,4 g orally four times daily	Decrease enterohepatic recycling of thyroid hormones

Do's

• Start immediate treatment with a beta blocker

• Acetaminophen should be used instead of aspirin

• Iodine administration should be postponed for at least one hour after administration of thionamide

• Propranolol, PTU, and methimazole can be administered through a nasogastric tube

Don'ts

• The content in this section is in bullet points.

References

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