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Tesi etd-09012019-122930


Thesis type
Tesi di laurea specialistica LC6
Author
BERNARDI, MARCO
URN
etd-09012019-122930
Title
SUBCLINICAL THYROID DISFUNCTION IN CARDIOLOGIC PATIENT AFTER NONINVASIVE CORONARY CT SCAN
Struttura
RICERCA TRASLAZIONALE E DELLE NUOVE TECNOLOGIE IN MEDICINA E CHIRURGIA
Corso di studi
MEDICINA E CHIRURGIA
Supervisors
relatore Prof. Caramella, Davide
correlatore Dott. Bianchi, Massimiliano
Parole chiave
  • thyroid
  • iodinated contrast media
  • ct
Data inizio appello
24/09/2019;
Consultabilità
Secretata d'ufficio
Riassunto analitico
ABSTRACT

Introduction
Iodine is an essential micronutrient for the thyroid gland to synthesize thyroid hormones. A normal adult utilizes about 80 μg/day of iodine to maintain adequate thyroid hormone production, which represents an intake of approximately 150 μg/day of iodine after accounting for fecal and urinary losses. With the increased use of computed tomography (CT) scans using iodinated contrast media (ICM) in recent decades, excess iodine exposure has increased. Worldwide, it is estimated that 80 million doses of ICM are administered annually. A typical dose of ICM contains approximately 15–37 g of total iodine, corresponding to several hundred thousand times the recommended daily allowance (RDA=150 μg/day). Iodine-induced thyroid dysfunction due to iodinated contrast agents has been described over the past several decades. The effects of ICM on serum thyroid function and urinary iodine clearance remains essential to monitor in patients at risk for developing hyperthyroidism or hypothyroidism following a CT scan. After ICM administration, iodine stores remain elevated for up to 4–8 weeks in patients with intact thyroids due to the high affinity of iodine to plasma proteins. The persistence of iodine overload could create severe consequences in patients affected by coronary heart disease. In fact, the hemodynamic homeostasis could be altered by the effects of an iatrogenic hypo/hyperthyroidism on myocardial function.

Purposes of the study
1. Assess the presence of thyroid dysfunction in a population of cardiac patients without known thyroid disease, admitted for noninvasive coronary CT angiography.
2. Evaluate the temporal changes in thyroid metabolism and urinary iodine excretion during the 12 months after the administration of ICM.

Materials and methods
The study enrolled 14 consecutives clinically euthyroid adult patients who were admitted to Radio Diagnostic Department of the University of Pisa to perform coronary CT scan. The patients were evaluated by urinary iodine concentration and thyroid function parameters before the CT scan and after 24 hours, 7 - 30 days and after 3-6-12 months.

Results
Patients were divided into three groups based on basal urinary iodine concentration (< 100 µg/L, deficiency; 100 – 300 µg/L, sufficiency; > 300 µg/L, excess): patients with normal urinary iodine concentration (n = 10 – Group 1); patients with reduced urinary iodine concentration (n = 3 – Group 2); patients with high urinary iodine concentration (n = 1 – Group 3).
All patients showed a dramatical increase of urinary iodine excretion at 24 h (> 2000 µg/L) until 1 week; after 1 month the urinary iodine started to decrease to normal value (average  SD = 211  128 µg/L). The patients with reduced basal urinary iodine concentration showed, at 6 months, superimposable value.
The TSH value showed an elevated increase above the normal range in 3 patients with a peak at 1 week (> 4 mUI/L, subclinical hypothyroidism). In the others, the TSH value, always in the normal range, showed a not significant increase with the maximum value at 1 week (1,95  0,82 vs 2,95  1,8 mUI/L; p = 0,07).
The thyroid hormones showed inverse physiological modification respect the TSH value at 1 week with a maximum decrease (fT3 4,14  0,59 vs 3,71  0,65 ng/L; fT4 1,14  0,16 vs 1,06  0,2 ng/dL). All thyroid function parameters showed values in the normal range after 1 month.

Conclusions
The fact that an overload of iodide may be administered by ICM administration is not novel. For this reason, international guidelines (ESUR 2018) recommend caution with the aim of limiting the risk of iatrogenic thyrotoxicosis only in patients with untreated Graves’ disease and in patients with multinodular goitre and thyroid autonomy, especially if they are elderly and/or live in an area of dietary iodine deficiency. As well as the renal function determination, the thyroid hormones dosage is not recommended in all patients who perform CT scan with ICM by the recent guidelines.
In our study is demonstrated that the iodine overload could create a widespread alteration of thyroid hormones concentration and urinary iodine excretion mostly after 1 week; it generates a clear subclinical hypothyroidism only in three patients belonging to Group 2 and in the others only a thyroid hormones modification in the normal range.
All data suggests that an iatrogenic iodine overload could be dangerous for patients affected by coronary heart disease and more attention must be considered for the thyroid metabolism in this susceptible group of patients beyond the International ESUR guidelines.
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