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L Druetta, H Bornet, G Sassolas and B Rousset

Thyroglobulin (Tg) present in the serum of normal individuals and patients with thyroid disorders could be partly newly synthesized non-iodinated Tg and partly Tg containing iodine and hormone residues originating from the lumen of thyroid follicles. With the aim of examining the contribution of the latter source of Tg to the elevation of serum Tg concentration in thyroid pathophysiological situations, we devised a procedure to identify thyroxine (T4) and tri-iodothyronine (T3) residues on Tg from unfractionated serum. A two-step method, basedon (i)adsorption of Tg on an immobilized anti-human Tg (hTg) monoclonal antibody (mAb) and (ii)recognition of hormone residues on adsorbed Tg by binding of radioiodinated anti-T4 mAb and anti-T3 mAb, was used to analyze serum Tg from patients with either Graves' disease (GD), subacute thyroiditis (ST) or metastatic differentiated thyroid cancer (DTC). Purified hTg preparations with different iodine and hormone contents were used as reference. Adsorption of purified Tg and serum Tg on immobilized anti-hTg mAb ranged between 85 and 90% over a wide concentration range. Labeled anti-T4 and anti-T3 mAbs bound to adsorbed purified Tg in amounts related to its iodine content. Tg adsorbed from six out of six sera from ST exhibited anti-T4 and anti-T3 mAb binding activities. In contrast, significant mAb binding was only observed in one out of eight sera from untreated GD patients and in 1 out of 13 sera from patients with DTC. The patient with DTC, whose serum Tg contained T4 and T3, represented a case of hyperthyroidism caused by a metastatic follicular carcinoma. In conclusion, we have identified, for the first time, T4 and T3 residues on circulating Tg. The presence of Tg with hormone residues in serum is occasional in GD and DTC but is a common and probably distinctive feature of ST.

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F Giammarile, C Houzard, C Bournaud, Z Hafdi, G Sassolas and F Borson-Chazot

OBJECTIVES: Somatostatin receptor scintigraphy (SRS) with (111)In-octreotide has been suggested as a potential tool for the detection of recurrent or metastatic differentiated thyroid cancer when no radioiodine uptake can be demonstrated in tumour sites. However, there is no consensus concerning the performance and clinical impact of this examination in such instances. DESIGN AND METHODS: A prospective study was undertaken to evaluate SRS in 43 patients (18 men, 25 women) with papillary (n=20), follicular (n=9), insular (n=6) and oncocytic (n=8) thyroid carcinomas with elevated serum thyroglobulin (Tg) levels and no detected radioiodine uptake. RESULTS: Evaluation criteria were interpreted in terms of an assumed presence of tumoural tissue. Sensitivity of SRS was 51%, clearly lower than that of conventional imaging procedures, and of positron emission tomography using [(18)F]-2-fluoro-2-deoxy-d-glucose, performed in a subset of 27 patients. In addition, we observed two false-positive foci of uptake of octreotide that corresponded to inflammatory pulmonary sites. The sensitivity was higher in patients with Tg levels greater than 50 microg/l (76%) for detecting mediastinal lesions (93%), and in patients with oncocytic cancer (88%). Finally, SRS changed treatment strategy in four patients. CONCLUSION: In differentiated thyroid cancer, SRS is a moderately sensitive method for the detection of lesions unable to concentrate iodine and appears useful only in patients with very high Tg levels or in oncocytic cancer.

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F Giammarile, Z Hafdi, C Bournaud, M Janier, C Houzard, C Desuzinges, R Itti, G Sassolas and F Borson-Chazot

OBJECTIVE: Dedifferentiation of thyroid cancer leads to an inability of thyroid cells to concentrate iodine. In these cases, imaging methods that allow an accurate detection of recurrence and/or metastases at an early stage are essential for an adequate management of patients. Positron emission tomography using [18F]-2-fluoro-2-deoxy-d-glucose and a dedicated (dPET-FDG) or non-dedicated (nPET-FDG) camera has been suggested as a potential tool for the detection of tumour foci. DESIGN AND METHODS: This prospective study was undertaken to evaluate nPET-FDG in 51 consecutive patients (18 men, 33 women) with differentiated thyroid cancer (33 papillary, 11 follicular, four insular and three oncocytic (Hurthle-cell) thyroid carcinomas). Selection criteria were high thyroglobulin (Tg) levels (>10 ng/ml off-levothyroxine treatment) and no detectable radioiodine uptake, on a whole body scan performed with a high dose, in the absence of iodine contamination. RESULTS: Results were interpreted in terms of assumed presence of tumoral tIssue. Sensitivity of nPET-FDG was similar to that of conventional imaging modalities (67%). False negative nPET-FDG (n=16) were observed mostly in cases of micro-lesions (lymph nodes or lung metastases). Conversely, nPET-FDG identified new tumoral sites in 11 cases. Better sensitivity was found for nPET-FDG in patients with Tg levels higher than 15 microg/l (P<0.05). On a patient basis, results of nPET-FDG were equivalent to that of dPET-FDG. Finally, nPET-FDG changed treatment strategy in seven patients. CONCLUSIONS: nPET-FDG has a high sensitivity for the detection of tumour sites in patients when pathological iodine uptake cannot be demonstrated and appears to be a useful method in patients with elevated Tg levels, especially when dedicated PET is either unavailable or impractical.

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G Sassolas, FB Chazot, P Jaquet, I Bachelot, P Chanson, CC Rudelli, JP Tauber, H Allannic, J Bringer, N Roudaut, V Rohmer, P Roger, JL Latapie, P Reville and M Leutenegger

OBJECTIVE: The prevalence of adult onset GH deficiency (GH-D) is poorly documented. Epidemiological data are now required to estimate the financial cost of GH treatment in adults. The aim of the present study was to estimate the prevalence of GH-D, from a cohort of 1652 adult patients with hypothalamo-pituitary diseases. DESIGN: The hormonal status of all patients presenting with pituitary diseaseand observed during the year 1994 in 15 endocrine units was retrospectively analyzed, irrespective of the date of disease onset, of the nature and date of pituitary investigations, and whether or not they included specific testing of the GH axis. Of the whole population of 1652 patients, a selected group (RG2) was chosen after exclusion of patients with active acromegaly (n=1414). RESULTS: GH stimulation tests had been performed in 549 patients of the RG2 group and a documented GH-D was found in 301. A relationship between the value of the GH peak and the number of pituitary deficits was evaluated. For instance, it was shown that 93% of patients with three deficits had GH-D. These results constituted the basis for estimating the number of GH-D in the group of untested patients. The number of GH-D deduced from the number of established GH-D (n=301) and from the number of GH-D hypothesized from other pituitary deficits (n=406) was 707 cases. Prevalence and annual incidence were calculated from data recorded in a referral center with a well-defined catchment area, Marseilles (Bouches du Rhone department). We projected a prevalence of 2638 for France and an annual incidence of 12 GH-D per million of the adult population.