I when compared to GD

Amiodarone is a popular drug in the management patients with cardiac rhythm abnormalities. The drug is rich in iodine and is inuence thyroid function due to the high iodine load. Amiodarone contains about 37% iodine by weight and the patient on daily dose of 200 mg, ingests 75mg of organic iodine. The drug under­goes further metabolic degradation releasing more iodine, approximately 6mg of free circulating iodine. Ultimately the patient receives about 20–40 times higher amount iodine daily. The clinical effects of amiodarone on thyroid function are both related hypothyroidism and hyperthyroidism. Amiodarone-induced hypothy­roidism (AIH) is common in iodine sufcient population [7]. AIT is prevalent in iodine-decient populations; with Hashimoto’s thyroiditis being an important risk factor. Type I AIT usually occurs in patient with subclinical autoimmune thyroid disorder leading on to developing overt Graves’ disease. Type II is toxic manifes­tations due to cellular destruction induced by excess iodine and later becomes hypothyroid. A combination of both types is not unusual (Type I, II, mixed). Amiodarone induced thyrotoxicosis has to be properly diagnosed and treated since thyrotoxicosis itself induces cardiac arrhythmias. Discontinuation of amio­darone with proper substitute is ideal and scintigram is good tool to make proper diagnosis (Table16.3).

A miniature gamma camera with sodium iodide crystal otherwise called the Gamma Probe is now in wide use. This cylindrical or conical shaped collimator mounted on a stand and helps to calculate the uptake quantitatively and helps to calculate the thyroid uptake in counts with the help of a computer software. There is no image and the report is interpreted as counts per minute (cpm).

1. Thyroid scan with MIBI as tracer helps to locate the nodule in the hyper func-

A uorodeoxyglucose positron emission tomography (FDG-PET) is now popular imag­ing used in assessment of extent of many malignancies. Now the imaging has applica­tions in many elds other than malignancy. The imaging is usually performed using vendor-specied simultaneous PET CT protocol. The image acquisition can be of the whole body or region specic according to the need. Ideally the patient is fasting over­night and the blood sugar level <150mg/dL and serum creatinine levels within the nor­mal ranges. The CT scan image acquisition precede the FDG administration.

FDG-PET imaging is not routinely performed as part of thyroid nodule evaluation. But a nodule incidentally detected on PET scan done for other indications stand higher chances of malignancy [9]. 18F FDG accumulates in neoplastic cells which use glu­cose as the source of energy source in proliferative activity. But FDG PET-CT is able to identify and characterize with accuracy small thyroid nodules (i.e., ≥5mm) and also cytological indeterminate thyroid nodule [10]. The 18F FDG PETCT scores over the qualitative FDG-PET is on regular use in assessment of advanced differentiated and poorly dif­ferentiated thyroid carcinoma especially when distant metastases in the presence of elevated thyroglobulin levels.

of the radioactive iodine, few controversies exist in selection of patients, goal of therapy, and dosage schedule.

I dosage to render patients euthyroid is not always possible and a higher

dose to render the patient hypothyroid is more practical.

1. Ensuring iodine avidity by a

I therapy (a mini­mum of 5 days for methimazole and 3 days for propylthiouracil) and are restarted 7 days after treatment.

The success rate of one sitting of low dose

I therapy for hyperthyroidism man­agement is 93% in our institute with adequate patient preparation. A second or third doses are required in high volume glands and those with orid Graves’ disease evidenced by a high technetium trapping function. Hypothyroidism sets in due course of time and levothyroxine supplementation is essential.

Patients with Graves’ ophthalmopathy may worsen following

I therapy. It is not unusual to develop ophthalmic complications following ablation. When Graves’ oph­thalmopathy is suspected a proper ophthalmology assessment to assess the clinical activity score is mandatory before scheduling for low dose in a dose 0.5mg to 1mg/kg body weight started a week before low dose

I therapy. Systemic steroid

1. The dosage of

I calculated based on volume of the thyroid gland calculated by

2. Otherwise, a xed empirical dosage is given.

There is no signicance evidence supporting dosage calculated has superiority over the xed dose regimen. Majority of patients receiving low dose therapy ends up in hypothyroid state irrespective of the dosage schedule adopted and a xed dose regimen is convenient to follow.

Those who show persistence of hyperthyroid state need additional doses of

which is planned 8–12 weeks after the initial ablation.

The common side effects include nausea, neck pain.

Side effects of low dose

pain lasting for few days. Thyroid storm had been reported rarely 1–14 days post-

I administration in patients with severe, uncontrolled hyperthyroidism and very large goiters. Worsening of ophthalmopathy has been reported in a small percentage of adults who have received

I, but now is controlled by prophylactic steroid. Symptoms of hyperthyroidism if any in the interval period can be readily controlled with adequate use of beta-blockers (usually oral metoprolol 20–40mg per day).

TSH (rhTSH) is a genetically engineered molecule containing thyrotropin Alfa (0.9mg in each vial) (Thyrogen by Genzyme). The molecule is commercially avail­able vials containing 1.1mg of thyrotropin Alfa, 36mg Mannitol, 5.1mg sodium phosphate, and 2.4mg sodium chloride. The drug is reconstituted prior to use with

1.2 mL of sterile water to deliver 1 mL injection from each vial. One milliliter reconstituted medication is injected intramuscularly in the gluteal region followed by the second injection 24 h later. There are no major side effects except for an occasional mild u-like symptoms. The common recommendations for rhTSH include for those patients intolerable to hypothyroid state, other major illness pre­venting a hypothyroid state and extensive functioning metastases [14].