NIV Congres

Case: We present a case of a 66-year old male patient who was referred to the outpatient clinic because of an elevated TSH (4.2 mU/l) and FT4 (26 pmol/l). His medical history reported a biopsy of his prostate because of benign disease. Medical history nor physical examination were suggestive for hyperthyroidism. His laboratory results showed TSH2. 1 mU/l as lowest value and 4.2 mU/l as highest value, for FT4 the lowest value was 26 pmol/l and the highest value was 33 pmol/l (normal upper limit 24). A total T4 was measured 164.8 nmol/l (n < 150). TSI and TPO antibodies were negative, T3 level was 2.4-2,8 pmol/l n < 2,5). The values of other hypophyseal hormones were normal:prolactin 278 mU/l, LH 3.4 U/l, FSH 5.4 U/l, morning cortisol 436 nmol/l, testosterone 11.9 nmol/l, IgF1 155 ug/l. Our differential diagnosis was secondary hyperthyroidism due to an pituitary adenoma or a default biochemical analysis. MRI scan with gadolinium was normal and thyroid scintigraphy showed an image of a thyroid with normal size with intense accumulation of the radiopharmacon without signs of multinodular struma or solitary adenoma. Human mouse antigen antibodies were negative. Therefore the pre-emptive diagnosis of thyroid hormone resistance was postulated. Analysis in the Erasmus Medical Centre (prof. T.J. Visser) showed a mutation in the THRB beta gene on position E460 K which was consistent with our hypothesis of thyroid hormone resistance. By coincidence the gene data bank of the academic hospital included 2 other patients with the same mutations of which one person had the same family name. As far as both patients knew they were not related. Resistance to thyroid hormone was identified in 1967 with the recognition of TH receptor beta gene mutations. Firstly this was the only known cause of resistance to thyroid hormone. Recently genetic defects that reduce the effectiveness of TH through altered cell membrane transport and metabolism were identified which broadened the spectrum of this syndrome. Laboratory findings suggestive for resistance for thyroid hormone are a high serum free T4 concentration and non-suppressed TSH in absence of secondary hyperthyroidism.