'Hockey stick' sign on 99m Technetium pertechnetate thyroid scan.

Sir,

Thyroid hemiagenesis is a very rare congenital abnormality, in which one thyroid lobe fails to develop. The true prevalence of thyroid hemiagenesis is not known, because the absence of one thyroid lobe does not usually cause clinical symptoms. The detection of hemiagenesis is usually incidental, when the evaluation of other thyroid disorders is requested. Hemiagenesis is estimated to be prevalent in about 0.02% of normal children.[12]

We present the 99 mTc-pertechnetate thyroid scan findings of a 17-year-old female patient, who presented with a history of neck pain of recent onset, radiating to the parotid region. She was referred for a thyroid scan to rule out subacute thyroiditis. She underwent a thyroid scan 20 minutes after intravenous administration of 5 mCi of 99 mTc-pertechnetate, and it revealed a classical ‘Hockey Stick’ appearance, suggestive of hemiagenesis of the thyroid, with absent left lobe and normal right lobe and isthmus [Figure 1]. The scan also ruled out subacute thyroiditis. The scan findings were subsequently corroborated by a neck ultrasound.

Figure 1

Classical ‘Hockey Stick’ appearance on 99mTc-pertechnetate thyroid scan suggestive of hemiagenesis of the thyroid with absent left lobe and normal right lobe and isthmus (Figure 1). The scan also ruled out subacute thyroiditis

Thyroidal hemiagenesis, with an isthmus present, has the appearance of a hockey stick on a 99mTc-pertechnetate thyroid scan. Absence of the left lobe is more common with a ratio of about 4: 1. A female to male ratio of 3: 1 is seen. Associated diseases reported in the existing thyroid lobe include differentiated thyroid cancer, hyperthyroidism, primary and secondary hypothyroidism, benign adenoma, multinodular goiter, hyperparathyroidism, and chronic thyroiditis. Some patients are found to be in a euthyroid state without any other abnormalities as in our reported case.[3] The most common disease of the remaining lobe is hyperthyroidism.