; Conte, Lucia1
; Repetto, Anna Maria2
; Gay, Stefano1
; Marroni, Paola2
; Mittica, Miranda1
; Mussap, Michele2
1 UO Clinica Endocrinologica, Azienda Ospedaliera Universitaria San Martino – IST, Genoa, Italy
2 UO Laboratorio Analisi, Azienda Ospedaliera Universitaria San Martino – IST, Genoa, Italy
Macro-TSH can accumulate in circulation, elevating TSH levels. Aim of this study was to evaluate the prevalence of mTSH in patients who had undergone thyroidectomy for cancer.
To date, 39 patients and 14 controls with benignant pathology have been evaluated. Thyroidectomy was performed in all subjects. In all but 2 cases Tg/calcitonin levels were indicative of cure. All subjects were on L-T4. Free-T4 and TSH were evaluated by ECLIA (Roche). MTSH was screened by adding PEG to serum.
The percentage recovery of TSH (RTSH%) after PEG-precipitation was regarded as an inverse expression of mTSH. RTSH% of <
20% was considered suggestive of mTSH. RTSH% was 32.8±8.5% in thyroid cancer patients and 35.7±11.8% in controls. RTSH% <
20% was found only in 2 cases (5%). In all patients, no correlation was found between RTSH% and age, sex, BMI, years since thyroidectomy, tumor stage, radioiodine therapy, Tg levels, TgAb state, body weight-related L-T4 posology, concomitant drugs or f-T4 and TSH levels. Limitations: data collection is still ongoing. Though arbitrary, the choice of a 20% cut-off for RTSH% is in line with literature data.
Free TSH levels after PEG precipitation are very low in all subjects. The presence of mTSH seems to be a rare phenomenon in thyroid cancer. Body weight seems to be the predominant determinant in L-T4 posology to maintain an adequate TSH. The evaluation of more serum samples could add further data in patients, in whom a balance is required between adequate TSH suppression and the avoidance of unnecessary hyperthyroxinemia