powerpoint : disorders of the thyroid gland
TRANSCRIPT
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