intrathyroid

The story

1. Proto-Indo-European*h₁én
2. Proto-Indo-European*h₁énteros
3. Latin*interus
4. Latinintrā
5. Englishintra-
6. Proto-Indo-European*dʰwer-
7. Proto-Hellenic*tʰurā
8. Ancient Greekθῠ́ρᾱ (thŭ́rā)
9. Ancient Greekθῠρεός (thŭreós)
10. Proto-Indo-European*weyd-
11. Proto-Indo-European*wéydos
12. Proto-Hellenic*wéidos
13. Ancient Greekεἶδος (eîdos)
14. Ancient Greekθῠρεοειδής (thŭreoeidḗs)
15. New Latinthyreoīdēs
16. Englishthyroid
17. English todayintrathyroid

From intra- + thyroid.