THYROIDBENIGNDISEASECONDITIONSGENERALSURGERY

Thyroid disease condition

1. BENIGN THYROID DISEASES PRESENTOR - Dr. Dharmendra Singh (PG) MODERATOR - Dr . Saurabh Singh sir

2. Embryology of Thyroid The thyroid gland originates from the median and lateral thyroid anlages  embryologic precursor tissues  which follow separate embryologic paths prior to fusing and forming a single gland Median thyroid anlage :- Appears as an epithelial proliferation in the floor of the pharynx between the tuberculum impar and the copula, arising at the level of the second branchial arch. As it descend, the median thyroid anlage becomes a bilobed diverticulum with a median tubal structure called the thyroglossal duct, which keeps the structure connected to the tongue. Lateral thyroid anlage :- Arises from the pharyngeal endoderm and fuses to the median anlage in the fifth week during its embryologic descent. The lateral thyroid anlage is comprised in part from cells of the ultimobranchial bodies, which originate from the fourth and fifth pharyngeal pouches which gives rise to calcitonin-secreting parafollicular C cells.

3. Anomaly in development Thyroglossal Duct Cyst :- The normal development and subsequent obliteration of the thyroglossal duct are connected to that of the hyoid bone. The thyroglossal duct does not completely obliterate and the epithelial duct cells remains Thus thyroglossal duct cyst may arise from a persistent connection between the thyroid gland and the foramen cecum Presentation : painless midline neck mass at or near the level of the hyoid, can also be found near the base of the tongue or at the thyroid gland proper. Occasionally, these cysts can become infected from oral bacteria from the tongue, and can also form fistulous sinuses to the skin. Sistrunk procedure is the surgical treatment of choice for thyroglossal duct cysts that become chronically infected.

4. Cont. 2. Ectopic Thyroid Tissue :- Aberrant thyroid tissue can be found anywhere along the normal path of development and descent of the thyroid gland, from the foramen cecum down to the anterior mediastinum

5. Anatomy of Thyroid The normal thyroid gland is reddish-brown in color and rubbery in texture, with an adult gland typically weighing about 20 g. Thyroid resembles the silhouette of a butterfly, with two lateral lobes connected by an isthmus draped over the upper trachea just caudal to the cricoid cartilage. Is typically 4 to 6 cm in height and 1.3 to 1.8 cm in both transverse and AP dimensions. Each lobe’s height extends from the level of the mid to upper aspect of the thyroid cartilage down to the 5 th to 6 th tracheal rings. Laterally, the lobe extends to the sternocleidomastoid muscle and carotid artery, with a small posterolateral projection or lump known as the tubercle of Zuckerkandl The capsule enveloping the thyroid also form separate “ pseudolobules ” within the parenchyma of the gland itself; these coalesce into a solid ligamentous structure at the posterolateral aspect of the upper trachea called the suspensory ligament of Berry The tubercle of Zuckerkandl and Berry ligament are relatively constant anatomic landmarks for identification of the distal recurrent laryngeal nerve (RLN), which typically runs just posterior to these structures

6. Blood supply The direction of the inferior thyroid artery as it enters the thyroid gland is another important landmark used for the identification of the RLN, which typically crosses the artery perpendicularly as it travels into the larynx

7. Venous drainage There are three main venous drainage pathways from the thyroid gland. The superior thyroid veins typically run parallel to the superior thyroid arteries and drain into the internal jugular veins. The inferior thyroid veins run in a caudal direction from the inferior poles of the thyroid lobes and drain into the innominate veins. The middle thyroid veins are highly variable but typically arise from the lateral aspect of the mid thyroid lobes; they drain into the internal jugular veins.

8. Lymphatics The bulk of lymphatic drainage from the thyroid first goes to the perithyroidal lymph nodes in the central neck collectively grouped as level VI, which includes the lymph nodes between the two carotid arteries and bounded by the hyoid bone superiorly and the sternal notch inferiorly. The lateral neck jugular lymph nodes ( IIa , III and IV) as well as those in the posterior triangle of the neck (particularly level Vb ) also drain lymphatics from the thyroid Skip metastases that avoid Level VI and extend directly from the primary tumor to the lateral neck are exceptional cases that occur in less than 15% of cases

9. Nerve supply

10. Nerve supply (cont.) Cernea classification: (classification of ELN in relation to sup. pole of thyroid) Runs >1cm from superior pole Runs <1cm from A: it’s above the gland B: it’s on the gland- High chances of Injury RLN Injury: (passes through the tracheoesophageal groove) M/c site of injury- BEAHR’S Triangle Laterally: Tracheoesophageal groove Medially: Common carotid artery Superiorly: Inferior thyroid artery * Tubercle of zuckerlandl – Pointing tip towards RLN U/L injury: Hoarseness of voice (recovers in 3 months) B/ L injury: Stridor (d/t cords in cadaveric position) 1 st : Reintubate  wait for 24-48 hours t hen attempt to extubate with entire team for tracheostomy *After few months  if its permanent damage  ARYTENOIDECTOMY/ LATERALIZATION of CORD ( Thyroplasty )

11. THYROID ENLARGEMENT Normally Thyroid gland is impalpable GOITRE – Generalised enlargement of thyroid gland

12. CLASSIFICATION OF THYROID SWELLINGS

13. SIMPLE GOITRE AETIOPATHOGENESIS Stimulation due to increased TSH Decreased level of circulating thyroid hormones or due to inappropriate secretion from microadenoma in ant. Pituitary.  MC factor is dietary deficiency of iodine (endemic goitre)

14. Causes of Simple Goitre: Endemic goitre -iodine deficiency Dyshormonogenesis or Enzyme deficiency Goitrogens – vegetables of brassica (cabbage

15. STAGES OF GOITRE FORMATION Persistent TSH stimulation Diffuse hyperplasia of gland Later with fluctuation of TSH levels Mixed areas of active and inactive lobules develop. It is also probably due to increased sensitivity of follicular cells to TSH Active lobules become more vascular and hyperplastic

16. STAGES (CONT.) Haemorrhages occur with necrosis in the centre Nodule formation Centre of nodule is inactive and only margin is active , i.e. internodular tissue is active Formation of many nodules Multinodular Goitre

17. Diffuse Hyperplastic Goitre Initial Persistent increase in TSH levels causes diffuse hyperplastic goitre It appears in childhood in endemic areas. In sporadic cases usually occurs at puberty. Goitre is soft, diffuse, large enough to cause discomfort Colloid goitre occurs in late stage when TSH stimulation has fallen off

18. Multinodular Goitre Usually multiple nodules . Nodules may be colloid or cellular Cystic degeneration , haemorrhage and calcification are common Simple goitres are more common in female because of presence of oestrogen receptors in thyroid gland

19. Nodular goitre – clinical features Middle aged females (10:1) Slowly progressive disease Multiple nodule of different sizes found in both lobules , isthmus which is firm , nodular , non tender , moves with deglutition. Recent increase in size signifies malignant transformation or haemorrhage

20. INVESTIGATION THYROID FUNCTION TESTS (T3 , T4 , TSH) ULTRASOUND NECK FNAC – DONE FROM MOST DOMINANT NODULE CT SCAN OF THORACIC INLET - FOR TRACHEAL OR OESOPHAGEAL COMPRESSION

21. COMPLICATIONS TRACHEAL OBSTRUCTION DUE TO RETROSTERNAL GOITRE SECONDARY THYROTOXICOSIS CARCINOMA(USUALLY FOLLICULAR)

22. PREVENTION In endemic areas – introduction of iodised salts In early stages hyperplastic goitre may regress by giving thyroxine in a dose of 0.15 to 0.2 mg daily for few months

23. TREATMENT Nodular stage of simple goitre is reversible INDICATION FOR SURGERY Nodular goitre with features of underlying malignancy Difficulty in swallowing Cosmetic reason Tracheal compression

24. CHOICE OF SURGERY Total thyroidectomy with immediate and lifelong replacement of thyroxine Sub total thyroidectomy – involves partial resection of each lobe removing the bulk of gland , leaving upto 8gm of relatively normal tissue Total lobectomy – When one lobe is more significantly involve than the other

25. SOLITARY THYROID NODULE A Single Palpable nodule in an otherwise normal gland CAUSES Thyroid adenomas- Almost all thyroid adenomas are follicular follicular adenomas can be colloid (commonest type , do not have potential for microinvasion ) Fetal ( has potential for microinvasion ) Embryonal ( has potential for microinvasion ) Hurthle cell (has potential for microinvasion ) Hyalinising trabecular adenoma

26. Causes – contd Carcinomas Papillary ( commonest) , follicular , medullary , anaplastic Thyroid cyst Thyroiditis presenting as solitary nodule

27. Types of solitary thyroid nodule TOXIC SOLITARY NODULE (3-5%) NON TOXIC SOLITARY THYROID NODULE – BASED ON RADIO ISOTOPE STUDY HOT NODULE – AUTONOMOUS TOXIC NODULE . NODULE IS HYPERACTIVE WARM NODULE – NORMAL FUNCTIONING NODULE COLD NODULE – NON FUNCTIONING NODULE

28. CLINICAL FEATURES SINGLE PALPABLE NODULE, SMOOTH , FIRM RAPID ENLARGEMENT OF THYROID NODULE CAN BE MALIGNANT TRACHEAL DEVIATION TOWARDS OPPOSITE SIDE CONFIRMED BY TRAIL SIGN , THREE FINGER TEST X RAY – NECK. COMMONEST SITE - JUNCTION OF ISTHMUS WITH ONE OF THE LATERAL LOBES

29. INVESTIGATIONS USG – NECK - Size , number , echogenecity , solid or cystic , vascularity , presence of significant lymph node , micro calcification , cystic/necrotic changes FNAC – US guided Thyroid function tests Radioisotope study Power Doppler- is done to know the vascularity of gland X ray neck – Tracheal deaviation CT SCAN / MRI - Vascularity / retrosternal extension

30. TREATMENT Non toxic benign nodule – observation without any therapy. Annual clinical examination + US neck for follow up. Increase in diameter more than 2mm - FNAC and Hemithyroidectomy Solitary toxic nodule – initially Anti Thyroid drugs and then radioactive iodine therapy (5mcurie) Colloid nodule - observation or hemithyroidectomy (cosmetic , pain or increase in size) Risk of malignancy Total Thyroidectomy

31. RETROSTERNAL GOITRE Arise from lower pole of nodular goitre, from ectopic thyroid tissue. If neck is short and pretracheal muscles are strong , - ve intrathoracic pressure tends to draw the goitre into the superior mediastinum. Obstructive symptoms - dyspnea , cough and stridor, dysphagia, engorgement of neck veins, recurrent laryngeal nerve paralysis PEMBERTON SIGN +VE Xray - soft tissue shadow in superior mediastinum, deviation and compression of trachea

32. INVESTIGATIONS RADIOACTIVE IODINE STUDY IS DIAGNOSTIC (I 123) CT / MRI THYROID FUNCTON TESTS CHEST X RAY – SOFT TISSUE SHADOW BARIUM SWALLOW CHEST X RAY – ESOPHAGEAL INDENTATION

33. TREATMENT SURGICAL REMOVAL OF RETROSTERNAL THYROID IS DONE . CAN BE REMOVED THROUGH AN INCISION IN NECK. IN CASE OF LARGE RETROSTERNAL EXTENTION OR IN MALIGNANT TYPE MEDIAN STERNOTOMY IS DONE

34. THRYOGLOSSAL CYST SWELLING OCCURING IN NECK IN ANY PART ALONG THE LINE OF THYROGLOSSAL TRACT FAILIURE OF THYROGLOSSAL DUCT/TRACT TO OBLITRATE COMPLETELY CLINICAL FEATURES: SWELLING IN MIDLINE,TOWARDS THE LEFT MOVES WITH DEGLUTITION AS WELL AS PROTRUSION OF TONGUE SMOOTH, SOFT, CYSTIC , NONTENDER,MOBILE , TRANSTILLUMINANTS INVESTIGATIONS : RADIOISOTOPES STUDY ULTRASOUND NECK THYROID FUNCTION TEST FNAC

35. TREATMENT SISTRUNK OPERATION EXCISION OF CYST WITH FULL TRACT UPTO FORAMEN CAECUM ALONG WITH REMOVAL OF CENTRAL PART OF HYOID BONE IF NO NORMAL THYROID GLAND LEFT , MAINTAINENCE DOSE L – THYROXINE – 0.1 MG OD LIFELONG GIVEN

36. THYROGLOSSAL FISTULA IT IS ACQUIRED CONDITION CAUSE – Either infection of thyroglossal cyst which burst open or after inadequate removal of cyst. HOOD SIGN – Is characteristic Secretes mucous discharge INVESTIGATION Fistulogram Radioisotope study TREATMENT Sistrunk operation

37. THYROTOXICOSIS Hyperthyroidism –term used for over production of thyroid hormones Hyperthyroidism is one of the causes of thyrotoxicosis Thyrotoxicosis is a symptom complex due to increased levels of thyroid hormones It refers to biochemical and physiological manifestations of excessive thyroid hormones

38. CLINICAL CLASSIFICATION Diffuse toxic goitre (Graves’ disease, Primary thyrotoxicosis) Toxic nodular goitre (Secondary thyrotoxicosis)  Toxic nodule Hyperthyroidism due to rarer causes

39. Diffuse toxic goitre ( Grave’s Disease ) A Diffuse vascular goitre appearing at the same time as the hyperthyroidism, usually occurs in younger women and is frequently associated with eye signs. The syndrome is that of primary thyrotoxicosis 50 % family history of autoimmune endocrine diseases. Whole functioning thyroid tissue is involved Hypertrophy and hyperplasia due to abnormal thyroid stimulating antibodies (TSH- RAb ) that bind to TSH receptor sites and produce a disproportionate and prolonged effects.

40. TOXIC NODULAR GOITRE Simple nodular goitre is present for a long time before the hyperthyroidism, usually in the middle-aged or elderly, and very infrequently associated with eye signs The syndrome is that of secondary thyrotoxicosis.  In many cases- nodules are inactive Inter nodular thyroid tissue – over active However, in some toxic nodular goitres, one or more nodules are overactive and here the hyperthyroidism is due to autonomous thyroid tissue as in a toxic adenoma

41. TOXIC NODULE A solitary overactive nodule It may be part of a generalised nodularity or a true toxic adenoma. It is autonomous and its hypertrophy and hyperplasia are not due to TSH-R Ab. TSH secretion is suppressed by the high level of circulating thyroid hormones and the normal thyroid tissue surrounding the nodule is itself suppressed and inactive

42. CLINICAL FEATURES 8 times more common in women GI SYMPTONS CVS SYMPTONS NEUROMUSCULAR SYMPTONS PSYCHIATRY SYMPATHETIC OVERACTIVITY -

43. EYE SIGNS LID RETRACTION Von Graefe's sign -It is inability of the upper eyelid to keep pace with the eyeball when it looks downwards to follow the examiner’s finger Stellwag's sign - Absence of normal blinking . First sign to appear. Joffroy’s sign Moebius' sign Dalrymple's sign Naffziger sign -With patient in sitting position and neck fully extended, protruded eyeball can be visualized when observed from behind

44. INVESTIGATION Thyroid function tests - T3 , T4 INCREASES TSH-UNDETECTABLE Radioisotope study – I 131 more uptake – hot nodules TRH estimation ECG- cardiac involvement Total count and neutrophil count Thyroid antibody estimation

45. TREATMENT Relief of symptoms Beta blocker- control cardiovascular manifestation Calcium channel blocker Oral rehydration Antithyroid drugs Methimazole 20 – 40 mg OD (blocks thyroid hormone synthesis)

46. Carbimazole 5-10 mg three times a day Propyl thiouracil 200 mg three times a day (blocks thyroid hormone synthesis as well as blocks peripheral conversion of T4 to T3) Iodides – reduce vascularity Steroids

47. THYROIDECTOMY HEMITHYROIDECTOMY PARTIAL THYROIDECTOMY SUBTOTAL THYROIDECTOMY NEAR TOTAL THYROIDECTOMY TOTAL THYROIDECTOMY HARTLEY DUNHILL OPERATION

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