A case of Resistance to Thyroid Hormone without mutation in the thyroid hormone receptor beta.
BACKGROUND
Resistance to Thyroid Hormone (RTH) is a condition caused by tissue hyposensitivity to the effects of circulating thyroid hormone, and may be misdiagnosed as hyperthyroidism.


OBJECTIVE
We report the first case of RTH in an Irish patient highlighting the clinical features and the pathophysiological mechanism underlying the characteristic laboratory abnormalities found in the condition.


METHODS
We describe an isolated case of RTH initially misdiagnosed as hyperthyroidism, and detail the investigations which ultimately led to the correct diagnosis. Genetic screening of the thyroid hormone receptor beta gene was performed.


RESULTS
Thyroid function tests including T3 suppression test and TRH-stimulation test suggested a diagnosis of RTH. Genetic testing failed to demonstrate a mutation in the thyroid hormone receptor.


CONCLUSIONS
RTH is a rare inherited condition that may be misdiagnosed as hyperthyroidism. The case we describe most likely results from a de novo mutation in an as yet undiscovered gene. RTH should be considered in patients with elevated thyroid hormone levels and normal TSH so that unnecessary and potentially harmful treatment can be avoided.
McDermott
J H
JH
Depts of Endocrinology, Royal College of Surgeons in Ireland, Connolly Hospital, Blanchardstown, Dublin, Ireland.
Agha
A
A
McMahon
M
M
Gasparro
D
D
Moeller
L
L
Dumitrescu
A M
AM
Refetoff
S
S
Sreenan
S
S
D000328:Adult; D004252:DNA Mutational Analysis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D009154:Mutation; D010911:Pituitary Neoplasms / Q000175:diagnosis*; D018570:Risk Assessment; D012720:Severity of Illness Index; D013960:Thyroid Function Tests; D037042:Thyroid Hormone Receptors beta / Q000235:genetics*; D018382:Thyroid Hormone Resistance Syndrome / Q000175:diagnosis* / Q000235:genetics; D013963:Thyroid Hormones / Q000378:metabolism
D037042:Thyroid Hormone Receptors beta; D013963:Thyroid Hormones