Being told at a health check-up that there is a nodule in the thyroid can leave a person uneasy, even after hearing that it is not large. The longer the time until the next check feels, the more a person may find themselves touching their neck, wondering whether it will grow in the meantime. In short, the follow-up interval is set not by the size of the nodule but by its shape and risk level on ultrasound, and being advised of a long interval is closer to meaning the nodule is stable than that it is being neglected.
This article sets out how follow-up intervals are divided by risk level, and which signs mean a person should visit the clinic first rather than waiting for the next appointment.
Why are check intervals set by shape rather than nodule size?
The risk level of a thyroid nodule is classified by its appearance on the ultrasound image. Depending on whether the margins are clear and the nodule is fluid-filled, or whether it looks taller than it is wide or contains fine calcifications, the same nodule can be placed in different risk categories, and this classification sets the time of the next check.
The American Thyroid Association guidelines also set this shape classification, rather than size, as the primary criterion for advising when the next check should be, and it is common for two people with nodules of similar size to be given different recheck dates. Shape is the key reason for the difference in advice.
- Margins and internal form — whether the margins are clear and the nodule is fluid-filled is checked first
- Vertical elongation — whether the nodule is taller than it is wide is assessed as well
- Fine calcification — whether fine calcifications are visible on ultrasound decides the classification
How does the follow-up interval change with the risk level?
Nodules with suspicious findings are advised to be rechecked within 12 months, and low- or intermediate-risk nodules are monitored at intervals of 12 to 24 months. This is because nodules with a low chance of change do not need to be examined just as often. In this way, the risk level decides the timing of the check.
When the risk is very low, patients may be advised to have the check after 24 months or told that repeat checks are not needed, and if there has been no change for several years the interval may be extended further. Being advised of a longer interval does not mean the condition has worsened; it means the nodule is staying stable.
- Suspicious findings — patients are advised to recheck within 12 months
- Low or intermediate risk — the nodule is monitored at intervals of 12 to 24 months
- Very low risk — checked after 24 months, or repeat checks may not be needed
Does a long check interval mean the nodule is being neglected?
A longer interval between checks means there has been no clear change in shape or size over that time, and the longer a nodule has stayed stable over several years, the more the next interval is adjusted to be longer. There is no need to misread a longer interval as meaning the nodule no longer needs to be watched.
A meaningful change is defined as growth of more than 20% in two or more of the three dimensions, together with an increase of at least 2 mm. A difference of around 1 to 2 mm may be measurement error, and the society's guidelines advise that this alone is no reason to bring the scheduled interval forward.
Which signs mean you should visit the clinic before your next appointment?
Having an appointment date still ahead does not mean that changes appearing in the body should also wait. If the voice stays hoarse or changed, or a new sensation of something catching when swallowing saliva appears that was not there before, it is safer to have it checked first, regardless of the scheduled interval.
If the lump has visibly grown or feels firmer than before when touched, this too is a sign to be examined first. When the lower part of the neck appears to bulge or a hard mass can be felt, or when there is a family history of thyroid cancer or nodules, attention should also be paid to changes.
- Voice change — when hoarseness or a changed voice persists, do not wait for the appointment date
- Catching sensation when swallowing — a new feeling of something catching when swallowing saliva needs to be checked first
- Change in lump size or firmness — if it visibly grows or hardens, it is examined earlier than scheduled
