A UK reported case of Graves’ disease with thyroid hemiagenesis

Abstract

We present a rare case of a 31-year-old patient with Graves’ disease with agenesis of the left thyroid lobe. The patient was managed with a right hemithyroidectomy and isthmusectomy as definitively treatment of Graves’ disease. The patient had an uneventful postoperative outcome and the histology was benign and consistent with Graves’ disease. This is a rare case in the literature of Graves’ disease with unilateral thyroid agenesis, and to our knowledge is the first reported case from the UK.

Background

Thyroid hemiagenesis is a very rare developmental defect of the thyroid gland.

The thyroid originates from endoderm in the embryological pharynx before descending into the normal anatomical position in the anterior neck. It is after this descent that the rudimentary thyroid will grow laterally to form the left and right lobes. Congenital abnormalities of the thyroid architecture can affect either the decent from the foramen caecum or by the agenesis of a thyroid lobe. The former is more common, resulting in thyroglossal cysts and the latter very rare. The aetiology of thyroid agenesis remains unexplained.¹

Many patients with thyroid hemiagenesis are euthyroid and asymptomatic and thus diagnosis is difficult unless identified incidentally, this often occurs in the investigation of concurrent thyroid disease.^2–4

Hemithyroid agenesis has been described in conjunction with concurrent thyroid pathology from autoimmune disease to malignancy.⁵ We present a case of left-sided thyroid hemiagenesis with Graves’ disease.

Case presentation

A 31-year-old woman was referred to ENT clinic for assessment for surgical management of Graves’ disease after she remained poorly controlled on maximal medical therapy. She had a family history of thyroid disease with both her mother and grandmother suffering from Graves’ disease.

Investigations

Initial examination of the neck revealed an asymmetric thyroid gland with a palpable right lobe and no obviously palpable left lobe.

Initial biochemical investigations demonstrated hyperthyroidism with a suppressed thyroid stimulating hormone (TSH <0.01 mIU/L), a raised free T4 level (Free T4=27.2 pmol/L) and a raised free T3 level (Free T3=11.4 pmol/L) and TSH receptor stimulating antibodies were raised (TSH receptor stimulating Ab=2.5 μ/L).

Nuclear medicine thyroid scan with technetium 99 m pertechnetate was performed prior to ultrasound and showed uniform uptake within the right thyroid lobe and isthmus with absent uptake on the left suggestive of an absent left thyroid lobe (see figure 1).

Figure 1.

Techneutium 99 nuclear medicine scan. High uptake throughout the right lobe with the absence of uptake on the left consistent with an absent left lobe.

Ultrasound findings confirmed the nuclear medicine findings identifying no left thyroid lobe with a right thyroid lobe and isthmus reported as appearing unremarkable with no evidence of nodularity. There was no abnormal lymphadenopathy identified (see figure 2).

Figure 2.

Ultrasound scan demonstrating a right lobe and isthmus and completely absent left lobe.

Treatment

The patient had undergone 18 months of medical therapy with carbimazole; however, she remained biochemically hyperthyroid and symptomatic, experiencing tremor and palpitations. Beta-blockers were contraindicated as a trial resulted in a respiratory wheeze and asthma exacerbation. While on carbimazole she developed signs of a peripheral polyneuropathy thought to be a result of her carbimazole therapy and thus it was discontinued and replaced with polypropylthiouracil. She remained symptomatic despite intensive medical therapy and the patient was referred for surgical management. Surgery was recommended following discussion with the patient, endocrinologist and surgeon in light of poor symptom control and to avoid radioiodine treatment in a young fertile women and in accordance with the British Association of Endocrine and Thyroid Surgeons Guidelines.⁶

She underwent a total excision of the right thyroid lobe and isthmus. Intraoperatively it was confirmed that no left lobe was present and no ectopic thyroid tissue was identified. The right recurrent laryngeal nerve was identified in the trachea-oesphageal groove and preserved. The left paratracheal region was inspected thoroughly and no evidence of thyroid tissue was identified. Figure 3 demonstrates the intraoperative view. Figure 4 demonstrates the intact specimen.

Figure 3.

Intraoperative view of right thyroid lobe/isthmus and absent left thyroid lobe.

Figure 4.

Intact specimen of right thyroid lobe and isthmus and absent left thyroid lobe.

Histopathology of the surgical specimen identified a 50x20x15 mm right lobe and an isthmus measuring 30x10x10 mm. Macroscopically unremarkable thyroid parenchyma was seen in both the isthmus and right lobe, and microscopy showed lymphocytic thyroiditis compatible with Graves’ disease with extensive lymphoid proliferation with germinal centre formation and benign follicles. There was no evidence of malignancy or oncocytic change.

Outcome and follow-up

Postoperative recovery was unremarkable with normal calcium and parathyroid hormone levels (PTH) in the normal range (serum-corrected calcium of 2.29 mmol/L and serum PTH of 3.7 pmol/L). The patient was discharged on the second day postoperatively with ongoing thyroid replacement therapy (levothyroxine 125 μg daily). The patient sustained no injury to the right recurrent laryngeal nerve, confirmed on flexible nasal endoscopy which showed normal bilateral vocal cord movements.

Discussion

Population-based screening suggests a prevalence of 0.02% of thyroid hemiagenesis. There is also a greater prevalence in females with a reported ratio of 3:1. Eighty per cent of cases affect the left lobe. with the majority of cases remaining asymptomatic.1–4 7 8 Our case is an example of symptomatic thyroid disease in the context of hemiagenesis.

In this case, preoperative imaging of the thyroid in the context of Graves’ disease was instrumental in diagnosis and allowed for an adjusted surgical plan. The diagnosis was highlighted by the initial nuclear medicine scan and ultrasound. Preoperative imaging in the case was useful in corroboration the diagnosis an enabling operative planning.

To our knowledge 16 cases of Graves’ disease in association with thyroid hemiagenesis have previously been reported worldwide.^{4 9–23} This is the first case reported from the UK.

Of the 16 reported other cases 4 had further associated pathology, 1 case had Hashimoto’s autoimmune thyroiditis and 1 case of congenital hypothyroidism prior to developing Graves’ disease.^{14 20}One case had an associated multinodular goitre and one papillary thyroid cancer.^{10 13}

Treatment modalities have varied throughout the other reported cases; six cases were treated with anti-thyroid drugs, two cases were treated with radioactive iodine therapy and three underwent surgical management. In the remaining five cases the course of management was not reported. In those patients undergoing surgery, two cases also failed to control thyroid function with medical therapy and one underwent thyroidectomy for an associated thyroid malignancy. All cases had successful treatment outcomes.^{4 9–23}

Treatment for Graves’ disease in the context of thyroid hemiagenesis has been treated in varying modalities however we believe surgery should be reserved for patients who are not controlled medically and in accordance to British Association of Endocrine and Thyroid Surgeons Guidelines.⁶

Learning points.

• Thyroid agenesis is a rare phenomenon.

• Thyroid agenesis may occur concurrently with underlying thyroid pathology.

• Although a rare phenomenon, preoperative imaging facilitates the diagnosis and surgical planning.