[Scintigraphically "hot" thyroid nodules mainly go hand in hand with a normal TSH]

Area of Science:

• Nuclear medicine
• Endocrinology
• Thyroidology

Background:

• International guidelines suggest thyroid scintigraphy only for subnormal TSH.
• Germany's lower iodine intake may increase autonomous thyroid nodules.
• Data on scintigraphy's utility with normal TSH in Germany are limited.

Purpose of the Study:

• To evaluate the spectrum of scintigraphically "hot" and "warm" thyroid nodules in Germany.
• To assess the TSH levels in patients with autonomous thyroid nodules.
• To determine the relevance of TSH levels for thyroid scintigraphy indications in Germany.

Main Methods:

• Multicenter analysis of 514 patients from 10 German nuclear medicine outpatient institutions.
• Inclusion criteria: unequivocally hyperfunctional nodules (≥1 cm) detected by (99m)Tc-pertechnetate scintigraphy.
• Parameters recorded: thyroid hormone levels, (99m)Tc-uptake (TcTU), nodule size, and autonomous nodular volume (V(aut)).

Main Results:

• Only 20% of patients with "hot" nodules had subnormal TSH levels.
• The majority of patients had TSH levels within the normal range (0.34–3.5 mU/l).
• No significant correlation was found between TSH levels and TcTU or V(aut).

Conclusions:

• Autonomous thyroid nodules in Germany frequently present with normal TSH levels.
• Scintigraphy findings for autonomous nodules are highly informative and can be safely classified as benign.
• Restricting scintigraphy to patients with subnormal TSH is not justified in Germany.