Diagnosis and Treatment > Signs and Symptoms
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Summary
Resistance to thyroid hormone-beta (RTHbeta) is a rare inherited syndrome characterized by variable reduced tissue responsiveness to the intracellular action of triiodothyronine (T3), the active form of the thyroid hormone. The presentation of RTHbeta is quite variable and mutations in the thyroid hormone receptor beta (THR-B) gene have been detected in up to 90% of patients. The proband was a 34-year-old Jordanian male who presented with intermittent palpitations. His thyroid function tests (TFTs) showed a discordant profile with high free T4 (FT4) at 45.7 pmol/L (normal: 12–22), high free T3 (FT3) at 11.8 pmol/L (normal: 3.1–6.8) and inappropriately normal TSH at 3.19 mIU/L (normal: 0.27–4.2). Work up has confirmed normal alpha subunit of TSH of 0.1 ng/mL (normal <0.5) and pituitary MRI showed no evidence of a pituitary adenoma; however, there was an interesting coincidental finding of partially empty sella. RTHbeta was suspected and genetic testing confirmed a known mutation in the THR-B gene, where a heterozygous A to G base change substitutes valine for methionine at codon 310. Screening the immediate family revealed that the eldest son (5 years old) also has discordant thyroid function profile consistent with RTHbeta and genetic testing confirmed the same M310V mutation that his father harbored. Moreover, the 5-year-old son had hyperactivity, impulsivity and aggressive behavior consistent with attention deficit hyperactivity disorder (ADHD). This case demonstrates an unusual co-existence of RTHbeta and partially empty sella in the same patient which, to our knowledge, has not been reported before.
Learning points:
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We report the coincidental occurrence of RTHbeta and a partially empty sella in the same patient that has not been previously reported.
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TFTs should be done in all children who present with symptoms suggestive of ADHD as RTHbeta is a common finding in these children.
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The management of children with ADHD and RTHbeta could be challenging for both pediatricians and parents and the administration of T3 with close monitoring may be helpful in some cases.
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Incidental pituitary abnormalities do exist in patients with RTHbeta, although extremely rare, and should be evaluated thoroughly and separately.
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Summary
TSH-secreting pituitary adenomas are rare and the optimal investigation and management is uncertain. We describe a case of a 43 year-old woman with a TSH-secreting pituitary adenoma, highlighting diagnostic testing and our use, pre-operatively of somatostatin analogue therapy, which induced biochemical euthyroidism and a reduction in tumour size.
Learning points
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The differential diagnosis of the syndrome of inappropriate TSH secretion is non-thyroidal illness, medications, assay interference due to heterophilic antibodies, thyroid hormone resistance and TSH-secreting pituitary adenoma.
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TRH stimulation test and triiodothyronine suppression test assist in differentiating thyroid hormone resistance and TSH-secreting pituitary adenoma.
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Somatostatin analogue therapy can induce biochemical euthyroidism and reduce tumour size.
