The purpose of this study is to examine tiny blood vessels in different thyroid nodules using advanced ultrasound. In the long term, we hope this can help doctors better tell the difference between types of nodules and more accurately decide who may need surgery.

In this study, the investigators use an advanced ultrasound technique called Super-Resolution Ultrasound of Erythrocytes (SURE) to map the microvasculature in the thyroid gland and thyroid nodules. This method provides much higher resolution than conventional ultrasound, allowing us to visualize and measure even the smallest blood vessels.

The investigators aim to explore whether this technique can help differentiate between various types of thyroid nodules - including benign and malignant - and possibly between hyper-, iso-, and hypofunctioning nodules, based on their microvascular characteristics.

Inclusion Criteria:

• Age over 18 years
• Written and verbal informed consent to participate in the study
• Patients with hypo-, iso-, or hyperfunctioning thyroid nodules
• Patients referred for thyroid surgery due to suspected malignant nodule (including Bethesda classification groups III, IV, V, and VI)
• Healthy volunteers - generally good health with no chronic illnesses

Exclusion Criteria:

• Pregnancy
• Inability to undergo the examination due to physical or mental limitations
• Desire to opt out of receiving information about new, significant health findings revealed during the study
• Healthy Participants:
• Thyroid disease, including nodules, as well as current or past conditions affecting the thyroid
• Medication that affects thyroid function

Healthy volunteers will be recruited through posters displayed at public institutions such as universities, libraries, and similar locations, as well as via the website https://forskningnu.dk/.

Patients will be recruited from the Department of Clinical Physiology and Nuclear Medicine, and the Department of Otorhinolaryngology, Head and Neck Surgery and Audiology, both located at Rigshospitalet, Denmark.