Case Report
TH Y R O ID G LA N D W ITH A SEPARATE LEFT LOBE
A ym elek Y a lın , P h.D. / Jasna G ü rb ü z, M .D . / M ehtap Yüksel, Ph.D.
D e p a rtm e n t o f A n a to m y , S c h o o l o f M e d ic in e , M a rm a ra U n iv e rs ity , Is ta n b u l, T urke y.
ABSTRACT
During routine dissection of a 50 year-old male
cadaver, we encountered a developmental anomaly of the thyroid gland having a left lobe connected to the isthmus by the thyroid fascia. Glandular tissue was not observed within the fascial connection. Right and left lobes were asymmetric, with heights of 83 mm and 52 mm, respectively. The gland was supplied by superior and inferior thyroid arteries, while the isthmus was supplied by branches of the right superior and inferior thyroid arteries. The thyroidea ima artery was not observed.
Key W ords:
Thyroid gland, isthmus, variationINTRODUCTION
The thyroid gland is the first endocrine gland appearing in about the third week of embryonic development. It begins to develop from median
endodermal thickening, about 24 days after
fertilization. This thickening is known as the
thyroid diverticulum (1,2). During embryologic
development, the thyroid gland descends in the neck connected to the tongue by the thyroglossal duct (3). By the seventh week, the thyroid gland usually
reaches its final site in the neck and the
thyroglossal duct normally degenerates and
disappears (1,2).
Normally the developed thyroid gland is enclosed by the pretracheal layer of the deep cervical fascia of the neck and has right and left lobes connected by a narrow, median isthmus (4).
CASE REPORT
During routine dissection of a 50 year-old male
cadaver an anomalous thyroid gland was
encountered. The thyroid gland was normally positioned between the fifth cervical and first thoracic vertebrae. Right and left lobes were asymmetric with heights of 83 mm and 52 mm, respectively.
The pretracheal layer of the deep cervical fascia enclosed the thyroid gland forming the thyroid fascia. The thyroid fascia was the only connection between the left lobe and the isthmus (Fig. 1).
The gland was supplied by superior and inferior thyroid arteries. The isthmus was supplied by the branches of the right superior and inferior thyroid arteries. The Thyroidea ima artery was not observed.
DISCUSSION
Although congenital functional defects of the thyroid gland (cretinism) are of great importance (5),
congenital morphological anomalies are not
insignificant.
Defects at the early period of morphogenesis lead to morphological anomalies which are relatively common and occur more frequently in females and on the left side (6-9).
In the current case, we came across the defect on the left side of the gland of a male cadaver. The left lobe was connected to the isthmus only by a fascia. The discontinuation of the glandular tissue between the isthmus and the left lobe could be misleading for a surgeon, suggesting a left lobe agenesis. Furthermore, the medial border of the left lobe could be
misdiagnosed as a pathological mass (1 0).
In unclear cases, the scintigram would be valuable for definitive diagnosis (7) to avoid an unnecessary surgical approach (6).
(A c c e p te d 5 N o v e m b e r, 1 9 9 9 )
36
T h y r o id g la n d w ith a s e p a r a t e le f t lo b e
F ig . 1 Photograph of the present case.
i: isthm us, pi: pyram idal lobe, fc: fibrous cord, sta: superior thyroid artery, *: the gap betw een the isthm us and the left lobe
The normal thyroid gland is almost always asymmetric and the right lobe may be twice as large as the left (10). In our case the right and left lobes are observed to be 83 mm and 52 mm in height, respectively. The pyramidal lobe represents a persistent portion of the inferior end of the thyroglossal duct (10). In this case, it was seen as a small prominence over the superior border of the isthmus and it was connected to the right part of the hyoid bone by a tiny fibrous cord. Hitherto, different abnormalities of the thyroid gland were reported, such as the ectopic gland (11-13) hemiagenesis or agenesis and thyroid associated anomalies (14-16,8).
In the current case the thyroid gland could be classified as a normally positioned asymmetric gland with a separate left lobe.
Sonography and computed tomographic scanning
may be useful in distinguishing between
developmental variations of the thyroid lobes and pathologic conditions (15).
REFERENCES
1. M o o re KL. T he d e v e lo p in g h u m a n . 4 th ed. P h ila d e lp h ia : W.B. S a u n d e rs C o m p 1 9 8 8 :1 8 4 -1 8 7 . 2. S a d le r TW. L a n g s m a n s m e d ic a l e m b ry o lo g y . 6 th ed.
B a ltim o re : W illia m s a n d W ilk in s 19 9 0 : 3 12 - 3 13. 3. H e m a n ic JK. A n a to m ija c o v je k a . V ol 2. 2 n d ed.
J u m e n a , Z a g re b : J u g o la v e n s k a M e d ic in s k a n a k la d a 19 7 9 :3 4 4 -3 4 7 .
4. W illia m s PL, W a rw ic k R, D yso n M, B a n n is te r L tl, G ray's A n a to m y . 3 7 th ed. E d in b u rg h : C h u rc h ill L iv in g s to n e , 19 8 9 ; 14 5 9 - 14 6 0 .
5. C o rlis s CE. P a tte n 's h u m a n e m b ry o lo g y ; E le m e n ts o f c lin ic a l d e v e lo p m e n t, f le w York: Me G raw- L lill B o o k C o m p 19 7 6 :3 3 0 - 3 3 6 .
6. B u rm a n KD. A d le r RA, W a rto fs k y L, H e m ia g e n e s is o f th e th y ro id g la n d . A m J S u rg 1 9 7 5 ;5 8 :1 4 3 -1 4 6 . 7. H a rad a T, H is h ik a w a Y, Ito K. A p la s ia o f o n e
th y ro id lo b e . A m J S u rg 19 7 2 ; 1 2 4 :6 1 7 -6 19. 8. G o llin g e r MRC. T h y ro id h e m ia g e n e s is w ith g o ite r.
JAM A 19 7 3 ;2 2 4 :1 2 8 . 9. B h a tn a g a r KP, H e ttle o n GS, W ag n e r CE, S u b is th m u s a c c e s s o ry th y ro id g la n d in m a n : A ca se r e p o rt a n d a r e v ie w o f t h y r o id a n o m a lie s . C lin A n a t 19 9 7 ; 10 : 3 4 1-3 4 4 . 10. H e tte r FH. E n d o c r in e s y s te m a n d s e le c te d m e ta b o lic d ise a se s. 3 r d ed. The CIBA C o lle c tio n o f M e d ic a l Illu s tra tio n s , Vol. 4. H e w J e rs e y : West C a ld w e ll. 19 7 4 ,-4 1 -4 5 .
1 1 . S h e m in RJ, M arsh JD , S h o e n FJ, B e n ig n in tra c a rd ia c th y ro id m a s s c a u s in g r ig h t v e n tric u la r o u tflo w tra c t o b s tru c tio n . A m J C a rd 1 9 8 5 ; 5 6 :8 2 8 - 8 2 9 .
12. D o n a E, A g o s to n i P, F lo re n tin e C. A c c e s s o ry th y ro id tis s u e in th e r ig h t v e n tric le . C h e s t 19 8 9 ,9 6 :4 2 4 - 4 2 5 .
13. L o HM, T seng YZ, T seng CD, C hu SH, C h u a n g SM, Wu TL. I n tr a c a r d ia c g o it e r : A c a u s e o f r ig h t v e n tr ic u la r o u t f lo w o b s t r u c t io n a n d s u c c e s s fu l o p e ra tiv e th e ra p y . A m J C a rd 1 9 8 4 ;5 3 :9 7 6 -9 7 8 . 14. Y ü k s e l M, Y ü k s e l E, K a y m a z F, F a ilu re o f th e is th m u s lo b e to fu s e in th e m id lin e . C lin A n a t 1 9 9 5 ;8 :3 3 -3 5 . 15. M e ln ic k JC , S te m k o w s k i PE, T h y ro id h e m ia g e n e s is (H o c k e y S tic k S ign): /I re v ie w o f th e w o rld lite ra tu re a n d a re p o r t o f f o u r cases. J C lin E n d o c rin o l M eta b
1 9 8 1 ;5 2 :2 4 7 - 2 5 !.
16. T a s h im a CK. A g e n e s is o f th e th y ro id . JAM A 1 9 7 3 ;2 2 4 :1 7 6 1 - 1 7 6 2 .
