Powerpoint : Disorders Of The Thyroid Gland

Gross anatomy is mandatory for the surgeon who is to operate on the thyroid gland

THYROID GLAND ANATOMY Two lobes connected by a narrow isthmus Very vascular organ- 5% of the CO Surrounded by a sheath derived from the

pretracheal layer of deep fascia The sheath attaches the gland to the larynx and the trachea Each lobe is pear-shaped, isthmus is across the midline in front of the 2nd,3rd,4th tracheal rings

THYROID GLANDANATOMY Antero-laterally: sterno-thyroid,omo-hyoid,

sterno-hyoid, SCM. Postero-laterally: carotid sheath Medially: larynx, trachea, pharynx, esophagus

THYROID GLAND BLOOD SUPPLY Arterial supply:

the

- STA from ECA, - ITA from thyrocervical from subclavian art. - thyroidea ima art. from aortic arch.

Venous drainage: STV, MTV, ITV into IJV

THYROID GLAND NERVES The right recurrent laryngeal nerve- recurs

around the SCA, crossing the ITA, before entering the tracheoesophageal groove.

The left recurrent laryngeal nerve-recurs

around the aortic arch-tracheoesophageal groove-penetrates the cricothyroid membrane.

Superior laryngeal nerve-intertwined with the

branches of the STA.

Right recurrent laryngeal nerve Passing around the SCA Oblique direction toward the tracheo-

esophageal groove Non-recurrent sometimes

Left Recurrent Laryngeal Nerve Always recurrent Close related to tracheo-esophageal groove Vertical direction Behind the post. aspect of the left lobe

NORMAL THYROID FUNCTION The follicular cells- T3, T4 T3, T4 bind with thyroglobulin, stored on the

gland until released onto the bloodstream

Release is under the control of TSH and TRH A feed-back mechanism regulating T3, T4

release is related to the level of circulating T3, T4.

HORMONAL ACTION The thyroid hormones:

-

increase the metabolic rate, increase the oxygen consumption, increase glycogenolysis, enhance the actions of catecholamines

HORMONAL ACTION The result is: Increase in the PR, CO and blood flow Nervousness, irritability, muscular tremor, muscle wasting

These effects can be blocked by the use of beta-blockers

HORMONAL ACTION The parafollicular or C-cells- produce

thyrocalcitonin Thyrocalcitonin action: - to lower serum calcium and phosphate concentration, - reduces bone resorption and the release of calcium and phosphate into the extracellular fluid, - in the kidney accelerates calcium and phosphate excretion:

CONGENITAL ANOMALIES Agenesis of the thyroid gland- commonest

cause of cretinism Incomplete descent of the thyroid glandlingual thyroid is the commonest form of incomplete descent Thyroglossal duct- persistence of a segment of the duct with cystic formation

THYROID GLAND DISORDERS CLINICAL EXAMINATION Hypothyroidism Symptoms: dry skin, cold intolerance, obesity,

constipation, deafness Signs: slow movements, cold and rough skin,

periorbital puffiness, slow PR

THYROID GLAND CLINICAL EXAMINATION Hyperthyroidism Symptoms: dyspnea on effort, palpitation,

tiredness, preferance for cold, sweating, nervousness, weight loss, good appetite Signs: palpable thyroid, exophtalmos, lid lag,

hyperkinesis, finger tremor, hot and moist hands, rapid PR

THYROID GLAND DISORDERS INVESTIGATIONS TSH- raised in primary hypothyroidism and

after treatment of thyrotoxicosis by surgery or radioiodine, - reduced in hyperthyroidism Free T3, T4- radioimmunoassays, Radioiodine uptake, Thyroid isotope scanning Ultrasonography, CT, MRI Fine needle aspiration cytology Thyroid autoantibodies (ab.to thyroglobulin)

Ultrasonography It is the most common and most

useful way to image the thyroid gland and its pathology.  The high sensitivity for nodules Poor specificity for cancer  

Thyroid imaging  Scintiscanning remains of primary importance in patients who

are hyperthyroid or for detection of iodine-avid tissue after thyroidectomy for thyroid cancer,  Sonography – largely used for the majority of patients who

require a graphic representation of the regional anatomy, smaller expense, greater simplicity, and lack of need for radioisotope administration.  Computer tomography (CT) and magnetic resonance imaging

(MRI) are more costly than sonography, are not as efficient in detecting small lesions, and are best used selectively when sonography is inadequate to elucidate a clinical problem

Sonogram of the neck in the transverse plane showing a normal right thyroid lobe and isthmus  L=small thyroid lobe in a

patient who is taking suppressive amounts of Lthyroxine, I=isthmus,  T=tracheal ring ( dense white arc is calcification, distal to it is artefact),  C=carotid artery ( note the enhanced echoes deep to the fluid-filled blood vessel), J=jugular vein, S=Sternocleidomastoid muscle, m=strap muscle

Sonogram of the left lobe of the thyroid gland in the transverse plane showing a rounded lobe of a goiter.  L=enlarged lobe,  I= widened isthmus,  T=trachea,  C=carotid artery ( note the

enhanced echoes deep to the fluid-filled blood vessel), J=jugular vein, S=Sternocleidomastoid muscle, m=strap muscles,  E=esophagus.

Sonograms showing

left lobe containing a degenerated thyroid nodule. Note the thick wall and irregularity. N=nodule, H=hemorrhagic degenerated region.

 The left panel shows an

anterior scintiscan of a euthyroid patient who had a tense nodule in the left thyroid lobe.  The nodule is "cold”nodule. The right panel shows a sonogram of the neck revealing that the nodule is a smooth-walled cystic structure.  C=cyst,  L=thyroid lobe.

Thyroid scintigram Autonomous adenoma in the

right lobe of the struma. The test substance accumulates almost exclusively in the range of the autonomous adenoma. The other areas of the struma show a considerable reduced accumulation of activity. 

Thyroid scintigram of a patient with Basedow hyperthyroidism The struma weighs 62

g and shows a highly increased uptake of 6.79% of the injected activity of TC99m. The distribution of the activity within the struma is regular. Lumps are not recognizable

Parathyroid adenoma  99Tcm pertechnetate

scintigram shows uptake by thyroid tissue only.  99Tcm sestamibi with uptake in both thyroid and parathyroid tissue.  The subtraction image locates the parathyroid adenoma behind the lower pole of the right lobe of the thyroid gland.

AM, 46-year-old woman, 2007 multinodular goitre and myasthenia gravis Thyroid profile (TSH-0.1 µUI/ml, fT4-1.2ng/dl), Thyroid total volume of 65.9 ml. (Prof. dr. C. Vulpoi)

Compressive goiter

Retrosternal goiter

Total thyroidectomy for MNG-2007, Myasthenia gravis aggravated Normal Chest

Normal thymus

Thymic scintigraphy Hypercaptation of 99mTc-tf. consistent with a thymoma

Antero- inferior mediastinal mass Thymectomy, 6 months following TT, june 2008 Paramedian low retrosternal mass

Well-encapsulated mass

Discussions In this case the thyroid lesion was more evident, and thus first

treated while MG was erroneously considered secondary to hyperthyroidism and consequently likely to remit following total thyroidectomy. On thymic scintigraphy, the hyperfixation in lower anterior

mediastinum raised the suspicion of thymoma, Pathology report of the surgical specimen (mixt thymoma -

Muller-Hermelink classification or AB type - WHO classification, with capsular microscopic invasion, Masaoka II stage).

GOITER ENLARGEMENT OF THE THYROID GLAND Simple goiter- diffuse hyperplastic goiter,

- nodular goiter Toxic goiter- diffuse (Grave’s disease), - toxic multinodular goiter, toxic solitary nodule Neoplastic goiter- benign, - malignant Thyroiditis- subacute (de Quervain’s), - autoimmune(Hashimoto’s), invasive fibrous thyroiditis (Riedel’s) - acute suppurative

SIMPLE GOITER Result of TSH stimulation, secondary, to

inadequate levels of T3, T4. TSH stimulation causes diffuse hyperplasia of the thyroid Iodine deficiency is a key factor in simple endemic goitre All types of goitre occur more often in women

Simple goiter Prevention- addition of iodine to table salt Treatment- prenodular stage- thyroxine,

- nodular stage with pressure effects- thyroidectomy

THYROID NODULES CLINICAL ASSESSMENT Most thyroid nodules are asymptomatic Acute painful swelling in the thyroid suggests

hemorrhage into a nodule Rapid growth of an existing nodule- malignancy A solitary nodule in a male- risk of cancer In the elderly, a rapid growing firm painful noduleanaplastic cancer Neck irradiation increases the risk of cancer

THYROID NODULES CLINICAL ASSESSMENT Most patients with a solitary thyroid nodule are

euthyroid A nodule in a hyperthyroid patient is unlikely to be malignant A hard fixed nodule is likely to be malignant but not uncommon for papillary cancer to be cystic and follicular cancer to be soft as result of hemorrhage A very hard nodule- calcified colloid nodule Lymphadenopathy- common finding in papillary and medullar carcinoma Reccurent laryngeal nerve palsy on the side of a palpable nodule- malignant infiltration

THYROID NODULES INVESTIGATIONS Measurement of T3, T4, TSH CXR- tracheal deviation or retrosternal

extension Isotope scanning- cold or hot nodule Ultrasonography- the structure Fine needle aspiration cytology

SOLITARY THYROID NODULE MANAGEMENT  Hyperthyroid- FNAC & isotope scan  Greater than 3 cm.- surgery  Less than 3 cm.- iodine therapy

 Euthyroid- FNAC  Benign-no pressure sy.-observe, repeat FNAC in 6 months  Benign- with pressure sy.- surgery  Thyoiditis- T4 treatment  Suspicious- surgery  Malinant- surgery  Inadequate FNAC- repeat  Cystic benign- observe,review in 6 weeks  Cystic malignant- surgery

MULTINODULAR GOITRE MANAGEMENT Hyperthyroid- iodine scan Large- ATD & surgery Small- iodine therapy

Euthyroid No dominant nodule-observe Dominant nodule-FNAC  Benign, no sy-observe  Malignant- surgery  Suspicious- surgery  Inadequate- repeat FNAC  Retrosternal- surgery  Cosmetic- surgery