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

THYROID GLAND ANATOMYTwo lobes connected by a narrow isthmusVery vascular organ- 5% of the COSurrounded by a sheath derived from the

pretracheal layer of deep fasciaThe sheath attaches the gland to the larynx

and the tracheaEach lobe is pear-shaped, isthmus is across

the midline in front of the 2nd,3rd,4th tracheal rings

THYROID GLAND-ANATOMYAntero-laterally: sterno-thyroid,omo-hyoid,

sterno-hyoid, SCM.

Postero-laterally: carotid sheath

Medially: larynx, trachea, pharynx, esophagus

THYROID GLANDBLOOD SUPPLYArterial supply: - STA from ECA,

- ITA from thyrocervical from subclavian art. - thyroidea ima art.

from the aortic arch.

Venous drainage: STV, MTV, ITV into IJV

THYROID GLANDNERVESThe 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 recurrentClose related to tracheo-esophageal grooveVertical directionBehind the post. aspect of the left lobe

NORMAL THYROID FUNCTIONThe 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 ACTIONThe thyroid hormones:

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

HORMONAL ACTIONThe result is:

Increase in the PR, CO and blood flowNervousness, irritability, muscular tremor,

muscle wastingThese effects can be blocked by the use of beta-

blockers

HORMONAL ACTIONThe parafollicular or C-cells- produce

thyrocalcitoninThyrocalcitonin 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 ANOMALIESAgenesis of the thyroid gland- commonest

cause of cretinismIncomplete descent of the thyroid gland-

lingual thyroid is the commonest form of incomplete descent

Thyroglossal duct- persistence of a segment of the duct with cystic formation

THYROID GLAND DISORDERSCLINICAL EXAMINATION

HypothyroidismSymptoms: dry skin, cold intolerance, obesity,

constipation, deafness

Signs: slow movements, cold and rough skin, periorbital puffiness, slow PR

THYROID GLANDCLINICAL EXAMINATIONHyperthyroidism

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 INVESTIGATIONSTSH- raised in primary hypothyroidism and

after treatment of thyrotoxicosis by surgery or radioiodine, - reduced in hyperthyroidism

Free T3, T4- radioimmunoassays,Radioiodine uptake,Thyroid isotope scanningUltrasonography, CT, MRIFine needle aspiration cytologyThyroid 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 imagingScintiscanning 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 L-thyroxine, 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 scintigramAutonomous 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 hyperthyroidismThe 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 scintigraphyHypercaptation of 99mTc-tf. consistent with a thymoma

Repeat CT scanAntero- inferior mediastinal massThymectomy, 6 months following TT, june 2008

Paramedian low retrosternal mass Well-encapsulated mass

DiscussionsIn 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).

GOITERENLARGEMENT OF THE THYROID GLANDSimple goiter- diffuse hyperplastic goiter,

- nodular goiterToxic 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 GOITERResult of TSH stimulation, secondary, to

inadequate levels of T3, T4.TSH stimulation causes diffuse hyperplasia of

the thyroidIodine 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 NODULESCLINICAL ASSESSMENT Most thyroid nodules are asymptomaticAcute painful swelling in the thyroid

suggests hemorrhage into a noduleRapid growth of an existing nodule-

malignancyA solitary nodule in a male- risk of cancerIn the elderly, a rapid growing firm painful

nodule- anaplastic cancerNeck irradiation increases the risk of cancer

THYROID NODULESCLINICAL ASSESSMENTMost patients with a solitary thyroid nodule are

euthyroidA nodule in a hyperthyroid patient is unlikely to be

malignantA 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 noduleLymphadenopathy- common finding in papillary

and medullar carcinomaReccurent laryngeal nerve palsy on the side of a

palpable nodule- malignant infiltration

THYROID NODULESINVESTIGATIONS

Measurement of T3, T4, TSHCXR- tracheal deviation or retrosternal

extensionIsotope scanning- cold or hot noduleUltrasonography- the structure Fine needle aspiration cytology

SOLITARY THYROID NODULEMANAGEMENTHyperthyroid- 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 GOITREMANAGEMENTHyperthyroid- iodine scan

Large- ATD & surgerySmall- iodine therapy

EuthyroidNo dominant nodule-observeDominant nodule-FNAC

Benign, no sy-observe Malignant- surgery Suspicious- surgery Inadequate- repeat FNAC Retrosternal- surgery Cosmetic- surgery