Unilateral thyroid agenesis (thyroid hemiagenesis) is a disorder where one lobe of the thyroid gland fails to develop normally and this is believed to be the rarest of all of the developmental thyroid anomalies [1].

The first reports of this entity appeared in 1866 by Handfield-Jones, in 1876 by Luschka and in 1886 by Ehlers [2]. Structural, congenital thyroid anomalies can be caused by either abnormal genesis or abnormal descent of part of the thyroid gland [2]. Thyroid hemiagenesis is a rare condition with only about 270 cases reported in the world literature up to 2003 [2] and still only about 300 cases , most as case studies by the year 2010 [3].

Here, a young male patient with some unusual features of thyroid hemiagenesis is presented and discussed.

A 21-year old Caucasian male was referred for a comprehensive examination due to the presence of asymptomatic, microscopic hematuria. The clinical examination was unremarkable with a blood pressure of 110/70 mmHg and no abnormalities noted on repeat urinalysis. Both his echocardiogram and renal ultrasound study was perfectly normal.

During thyroid ultrasonography complete absence of the isthmus and a severely hypoplastic left sided thyroid lobe was noted (Figures 1 and 2) with a normal right sided lobe (Figure 3). No clinical stigmata of thyroid disease was present. Biochemically he was in an euthyroid state (TSH=2.97 uIU/mL and free T4=15 pmol/L) and no antithyroid antibodies could be detected. The possible clinical implications and uncertainties related to this diagnosis will be discussed.

Figure 1: Transverse section through the thyroid—ultrasonography. The trachea is central with a normal right-sided thyroid lobe on the right and a rudimentary left-sided lobe on the right. Note the complete absence of the isthmus.

Figure 2: Rudimentary left-sided thyroid lobe.

Figure 3: Normal right-sided thyroid lobe.

There are several aspects of this case that merits discussion. Unilateral agenesis of a thyroid lobe is a rare congenital anomaly which afflicts women three times more commonly than men and in 80% of cases the left thyroid lobe will be the one affected [4]. Furthermore, in these cases of left thyroid lobe hemiagenesis about 50% will also have an absent thyroid isthmus [4]. In this young male the isthmus is completely absent (Figure 1), however some rudimentary tissue of the left lobe can be seen in Figures 1 and 2.

There are two clinical questions relating to unilateral thyroid agenesis:

The true incidence of this condition is unknown and probably completely underestimated, as it is usually an incidental discovery when the patient`s thyroid is examined due to the presence of pathology in the remaining lobe [5]. A vast array of pathologies have been described in the contralateral lobe and these include: carcinoma [6], subacute and chronic thyroiditis [7], Graves disease with ophthalmopathy [8], adenoma [5], multinodular goiter [5] and both hypo-and hyperthyroidism [5].

This of course leads to the second and most important clinical question: Does the presence of thyroid hemiagenesis predispose the afflicted patient to disease and malignancy in the remaining lobe? At present, this is not known, but it is a valid and concerning issue that needs to be clarified. Another valid clinical question emanating from this case is why a thyroid ultrasonographic examination was performed on a young man with hematuria? Kocak et al. [9] has shown a significant association between renal glomerular disease and autoimmune thyroid disease, thus the ultrasonographic examination in this patient referred with microscopical hematuria.

In conclusion, a case of a healthy 21-year old Caucasian male with incidentally discovered unilateral thyroid agenesis (thyroid hemiagenesis) is presented. Based on current literature, there is a real possibility that these patients may be at an increased risk for malignancy and/or functional disturbances in the remaining lobe. This important clinical question can only be answered by a properly powered study which will need a large population of screened cases with a proper duration of follow-up.