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ENDOCRINE IMAGING
yroid lymphoma:
While rare, lymphoma is a recognised thyroid pathology.
•
Ultrasound features may be similar to those of ATC.
•
Core biopsy is indicated to accurately categorise and dierentiate from ATC.
•
In all cases of suspected or conrmed malignancy, CT will demonstrate nodal staging of disease and local anatomical spread. It won’t, however, reliably dierentiate malignancy from
benign thyroid disease.
Benign Thyroid Disease
Multinodular goitre:
Ultrasound is the primary tool in assessing for pathological nodules in a large
•
thyroid.
Targeted FNA should be performed if indicated (see above).
•
CT is useful for providing anatomical assessment, particularly in relation to retroster-
•
nal extent and tracheal compression/deviation.
Graves’ disease:
On ultrasound, the thyroid appears hyper-reective, without nodules, and with
•
increased intrinsic blood ow on Doppler.
Hashimoto’s thyroiditis:
On ultrasound, the thyroid appears diusely hypoechoic, with occasional hyperechoic
•
brous bands, and with increased intrinsic blood ow on Doppler.
Parathyroid Glands
Imaging of the parathyroids is usually indicated in hyperparathyroidism to help identify an
enlarged or hyperfunctioning gland and to aid targeted surgical excision.
All imaging modalities can be used to complement each other for targeted exploration and
excision. While the superior parathyroid glands are fairly consistent in their position, the
inferior glands are much more varied.
Ultrasound
Ultrasound is quick and can identify an abnormal gland of at least 10 mm. Abnormal parathyroid glands have low echogenicity compared to the thyroid. However, the sensitivity and
specicity of ultrasound are user-dependent. In addition, ultrasound is less reliable when
there is an overlying multinodular goitre or the gland is in the tracheo-oesophageal groove
or the mediastinum.
Nuclear Imaging
Parathyroid scintigraphy is a common localisation scan technique using a radioisotope.
Technetium-99m (
molecules. It is taken up by both thyroid and parathyroid glands, but clearance is slower
with abnormal parathyroid glands. is property is taken advantage of by acquiring serial
planar images aer administration of tracer. Images can be subtracted from one another to
highlight the abnormal gland. While this is useful for visualising all parathyroid glands,
including ectopics, it does not provide spatial anatomical detail.
An alternate technique is SPECT (single-photon emission computed tomography), which
captures images using a gamma camera. SPECT images can be fused with standard CT
images (SPECT-CT) to provide useful anatomical localisation that surgeons can interpret
for surgical planning.
408 Head and Neck Endocrine Surgery
99m
Tc) is a radioisotope tracer bound to methoxyisobutylisonitrile (MIBI)
ENDOCRINE IMAGING
Computed Tomography (CT)
On contrast-enhanced CT, parathyroid adenomas show arterial phase enhancement with
subsequent rapid washout, whereas lymph nodes show gradual increasing enhancement.
is is taken advantage of in multiphase ‘4D CT’, a technique using serial CT sequences
acquired at various intervals aer contrast administration. However, use of this technique
means the patient is exposed to a higher radiation dose.
Pituitary
High-resolution MRI is considered the best modality for pituitary-related diagnostic purposes. It uses a dedicated multiplanar protocol of at least 3-mm slices in both coronal and
sagittal planes with pre- and post-contrast enhancement.
CT is usually used for pre-operative planning. e CT sinus protocol provides local nasal
and paranasal sinus anatomy for transnasal endoscopic surgery.
Adenomas
Pituitary adenomas can be macroadenomas (>1 cm) or microadenomas (<1 cm), and they
account for 10–15% of all intracranial tumours. ey usually originate from the anterior
pituitary, and macroadenomas oen extend through the diaphragma sellae.
Microadenomas are usually seen on imaging done for investigation of hormone dysfunction.
On T1-weighted MRI, they appear hypointense compared to normal gland, and they have
a slow uptake of contrast. erefore, serial post-contrast sequences can identify the slow
contrast enhancement.
Macroadenomas are usually evident due to damage to local structures. Bony remodeling
may be evident on CT if the macroadenoma is slow-growing, or the image may show invasion of bone. On MRI, macroadenomas usually appear isointense and enhance with contrast,
with central necrosis appearing hyperintense on T2-weighted images.
ere are several features to consider when dierentiating sellar masses:
Location: Is it intrasellar, suprasellar, infundibular, or in a combination of locations?
•
Connection: Is the mass separate from the pituitary gland?
•
Age of the patient
•
Meningiomas
Meningiomas mostly appear to arise from the parasellar areas and extend into the sella
turcica. ey are rare in children. ey typically appear hypo- to isointense on T1- and
T2-weighted images, with avid post-contrast enhancement. e hallmark sign is a ‘dural
tail’ (Figure 79.1).
Metastases
Metastatic involvement of the pituitary is rare, but lung and breast cancers are the most
likely sources. MRI ndings can be nonspecic and appear to be adenomas. Metastases can
appear as isointense lesions with local invasion of the cavernous sinus and sclerosis of the
sella turcica.
Craniopharyngioma
Craniopharyngiomas are the most common suprasellar masses in children. ere is
a bimodal age distribution, with peaks at 5–10 years and 50–60 years of age. e most
common presentation is that of a multilobulated, suprasellar, cystic mass with a solid
component and enhancing calcication. erefore, the mass appears hyperintense on
T2-weighted MRI due to the cystic component, with patchy enhancement on T1-weighted
post-contrast images. Rathke cle cysts can appear similar to craniopharyngiomas; however, they do not calcify.
Head and Neck Endocrine Surgery 409
EVALUATION AND INVESTIGATION OF THYROID DISEASE
Figure 79.1 Sagittal T1-weighted post-contrast image demonstrates a sella/suprasellar menin-
gioma. It enhances with contrast, and a ‘dural tail’ is seen as a linear enhancement extending
anteriorly. The normal pituitary is visibly separate and non-enhancing within the sella.
KEY POINTS
• Ultrasound is the primary modality for assessing thyroid and parathyroid glands.
• CT helps to provide anatomical detail when used with ultrasound or nuclear imaging
to aid surgical planning.
• Functional nuclear medicine imaging using
abnormal parathyroid glands.
• Primary imaging for pituitary glands is multiplanar MRI with pre- and post-contrast
sequences.
• Differentiating pituitary masses depends upon their location, the age of the patient,
and clinical signs and symptoms.
99m
Tc is useful to identify metabolically
80. EVALUATION AND INVESTIGATION OF THYROID DISEASE
CLINICAL EVALUATION OF THYROID DISORDERS
Functional Disorders
Functional disorders relate to the activity of the thyroid gland. ey aect 2% of the population, and they are more common in females (M:F ratio is 1:10).
Functional disorders are further divided into reduced thyroid function (hypothyroidism)
and increased thyroid activity (hyperthyroidism).
410 Head and Neck Endocrine Surgery
EVALUATION AND INVESTIGATION OF THYROID DISEASE
Hypothyroidism
e most common causes of hypothyroidism include chronic autoimmune thyroiditis
(Hashimoto’s thyroiditis) and iodine deciency.
Secondary hypothyroidism is commonly a result of hypothalamic or pituitary insuciency.
Symptoms
Patients usually present with a combination of symptoms that include fatigue, weight gain
with poor appetite, feeling cold, poor concentration and memory, hoarseness, shortness of
breath, abnormal sensation, constipation, dyspepsia, and altered menstruation.
Extreme hypothyroidism can result in coma, and congenital untreated hypothyroidism is
the cause of cretinism.
Signs
Common signs on physical examination are dry coarse skin, cool extremities, hair loss, and
bradycardia.
Rarer signs are Reinke’s oedema, myxoedema, delayed tendon reexes, carpal tunnel syndrome, pleural or pericardial eusion, and ascites.
Hyperthyroidism
e most common causes of hyperthyroidism are Graves’ disease, toxic multinodular goitre,
and toxic adenoma.
Symptoms
e common presenting symptoms of hyperthyroidism are weight loss, nervousness, anxiety, irritability, sweating, palpitations and tremor, thin skin, muscle weakness, and gastrointestinal and menstrual disturbances.
In extreme cases, the following symptoms can co-exist: tachydysrhythmia, pyrexia, vomiting, diarrhea, and mental agitation. is is a medical emergency known as thyroid storm and
requires urgent attention because it has a 20–50% mortality rate.
In Graves’ disease, eye symptoms can be evident due to thyroid ophthalmopathy; patients
present with exophthalmos, diplopia (particularly on upward gaze) in adduction, and a staring appearance.
Signs
On examination, signs of hyperthyroidism include perspiration, agitation, tremor; palmar
erythema, proximal muscle wasting, tachycardia, and/or atrial brillation.
In Graves’ ophthalmopathy, eye signs include axial proptosis with lid lag (von Graefe’s sign), lid
retraction (Dalrymple’s sign), conjunctival injection (Goldzeiher’s sign), and optical neuropathy.
yroid dermopathy (pretibial myxoedema with waxy, indurated, itchy skin that can spread
onto the foot and rarely other body parts) and thyroid acropathy (so tissue swelling of
hands, with occasional clubbing) are also signs of Graves’ disease.
Structural Disorders
Structural disorders are disorders aecting the thyroid parenchyma, resulting in thyroid
nodules.
ey are palpable in only 3–7% of the adult population, but their prevalence increases up to
70% following ultrasonographic assessment.
Thyroid Nodules
Most thyroid nodules are solitary, but they may be part of a multinodular goitre, which can
be focal, diuse, or associated with thyroiditis. yroid nodules can be benign or malignant,
with the latter being more common aer radiation exposure and with a family history of a
rst-degree relative with thyroid cancer.
Head and Neck Endocrine Surgery 411
EVALUATION AND INVESTIGATION OF THYROID DISEASE
Underlying Systemic Disorders
Struc tural thy roid disorder can ar ise as part of an underlying s ystemic disorder. Medullary ca ncer exists as part of the multiple endocrine neoplasia syndrome ty pe 2 (MEN 2) in 20% of cases.
yroid lymphoma can occur in isolation or as part of a wider haematological malignancy.
Symptoms
Patients commonly present with a painless, sometimes incidental, neck lump. Pain and rapid
increase in size are commonly associated with bleeding into a pre-existing cyst but can be
also suggestive of malignancy, especially if hoarseness co-exists. Large goitres can cause
compressive symptoms of dysphagia, dyspnoea, or stridor.
Signs
e most common examination nding is midline neck lump with elevation on swallowing. Lymphadenopathy and lump xation to surrounding structures are worrying features.
Retrosternal extension is suspected if the lower extent of the thyroid is impalpable. Tracheal
deviation can be seen secondary to compression and superior vena cava obstruction is seen
secondary to venous compression.
Venous congestion is elicited by raising both arms until they are touching the sides of the
face, causing cyanosis and respiratory distress (Pemberton’s sign).
Endoscopic signs include Reinke’s oedema, tracheal deviation, and direct invasion of the upper
aerodigestive tract.
Investigation of Thyroid Disorders
Biochemical Thyroid Function Tests
Serum Thyroid-Stimulating Hormone (TSH) Measurement
TSH is measured using antibody immunoassays. Generally, normal TSH rules out thyroid
dysfunction, but an elevated or suppressed TSH level should be considered in association
with the serum free thyroxine (FT4) and free serum triiodothyronine (FT3) levels. Primary
hypothyroidism causes elevated TSH, whereas primary thyrotoxicosis causes TSH suppression (Table 80.1). e normal reference range for TSH is 0.4–4.5 mU/L, but it can be aected
by pregnancy, age, genetic factors, obesity, and nonthyroidal conditions.
Table 80.1 Factors affecting the measurements of serum TSH, FT3, and FT
TSH FT4/FT
Primary hypothyroidism
Subclinical
Overt
Primary hyperthyroidism
Subclinical
Overt
Pituitary and hypothalamic disease
TSH-secreting
Destructive
Nonthyroidal illness (including psychiatric disease) Usually ↓ p
Pregnancy ↓ (1st trimester) Normal (1st trimester)
Drugs
• Dopamine, somatostatin, glucocorticoid
• Propylthiouracil, amiodarone
Thyroid hormone resistance ↑ ↑
Activating TSH receptor mutations ↓ ↑
Hydatidiform mole, choriocarcinoma ↓ ↑
TSH assay interference ↑ Normal
412 Head and Neck Endocrine Surgery
↑
↓
↑
↓
↓
-
4
3
Normal
↓ FT4, ↓ FT3 in 25%
Normal
↑ FT3 earlier; ↑ FT4 usually
↑
↓ FT4; FT3 normal or ↓
↓ (by 30% in last trimester)
Normal
FT3/FT4 ratio <0.3
EVALUATION AND INVESTIGATION OF THYROID DISEASE
FT3 and FT4 Measurement
FT3 and FT4 are measured using immunoassays. Subclinical hypo- or hyperthyroidism
involves elevated/suppressed TSH levels with normal FT4 and FT3 ndings. In subclinical
disease, TSH and FT4 should be retested aer 3 months to assess for disease progression.
TSH, FT4, and FT3 are measured during assessment of symptomatic thyroid disorders.
Routine neonatal TSH screening is performed with a heel-prick test.
In patients taking antithyroid medication for hyperthyroidism, FT4 monitoring is the test
of choice, as TSH can remain suppressed even aer treatment cessation. FT3 is the more
accurate measurement for patients taking propylthiouracil because its action blocks FT4
di-iodination.
In treatment with radioiodine, TSH and FT4 should be measured 6 and 12 weeks aer the rst
treatment and then every 3 months for the rst year, with annual measurements thereaer.
Monitoring of thyroxine replacement aer thyroidectomy or for primary hypothyroidism
evaluates TSH levels. TSH should be measured 2 months following initiation or adjustment
in the treatment regime to allow TSH stabilisation. Once the patient has stabilised, annual
TSH measurement will suce.
For secondary hypothyroidism, FT4 level is the only available monitoring measurement,
aiming for levels in the upper third of the reference range.
Causes of Thyroid Dysfunction
Thyroid Antibodies
yroid antibodies are found in around 10% of the healthy, euthyroid population. yroid
peroxidase (TPO) antibody immunoassays are usually used in isolation for diagnosis of
autoimmune thyroid disease, including overt hypothyroidism and Hashimoto’s thyroiditis.
yroglobulin antibody (TgAb) immunoassay is used for monitoring of dierentiated thyroid cancer recurrence postoperatively (see below).
TSH-receptor antibodies (TRAb) are measured in the diagnosis of Graves’ disease. ey have
a 95% sensitivity and 100% specicity for diagnosis of Graves’ disease in patients presenting
with hyperthyroidism.
High TRAb is a poor prognostic factor for development of Graves’ ophthalmopathy and can
be also used for diagnosing euthyroid Graves’ ophthalmopathy as well as predicting neonatal
Graves’ disease.
Erythrocyte Sedimentation Rate (Esr) and C-Reactive Protein (Crp)
ESR and CRP can be high in subacute thyroiditis, acute suppurative thyroiditis, and occasionally in Hashimoto’s thyroiditis.
Thyroglobulin (TG)
TG is a normal protein produced by thyroid follicular cells. e measurement of TG is only
reliable in a patient who has negative TgAb. A low serum TG level before radioiodine ablation
of any thyroid remnant has 94% negative predictive value for the absence of disease at future
follow-up. ere is no utility in measuring TG in the initial evaluation of a thyroid nodule.
Nature of Structural Thyroid Lesions
Scintiscanning
e use of radioiodine scintiscanning has declined because it less sensitive and specic than
thyroid blood tests and ultrasound.
Localisation of congenital anatomical thyroid defects
•
Dierentiating between destructive thyroiditis (subacute, postpartum) and hyperthy-
•
roidism (Graves’ disease or nodular thyroid disease), in which the isotope is reduced
(‘cold’—nonfunctional) and increased (‘hot’—functional), respectively
99m
123
Tc or
I were most frequently used for:
Head and Neck Endocrine Surgery 413
EVALUATION AND INVESTIGATION OF THYROID DISEASE
Identifying solitary hyperfunctioning nodules (increased uptake)
•
Monitoring of treated thyroid cancer (see Chapter 82, Management of Dierentiated
•
yroid Cancer)
Ultrasound (US)
US is recommended in the evaluation of all clinically signicant thyroid nodules and incidental ndings on other investigative modalities (see Chapter 79, Endocrine Imaging).
Nodules with normal or benign US characterist ics do not requ ire furt her investigation.
•
US is used for diagnostic purposes and to guide biopsies.
•
During follow-up, US is used for detection of locoregional recurrent thyroid cancer.
•
Fine-Needle Aspiration Cytology (FNAC)
FNAC is the gold-standard investigation in the evaluation of thyroid nodules aer US
assessment.
e cytological classication of ne-needle aspiration ndings introduced by the American
yroid Association (ATA) is called the Bethesda System, and the classication used by the
British yroid Association (BTA) is called the RCPath y System. Both systems are used to
guide clinicians in the management of thyroid nodules.
Nodules of y3f-4-5 (or Bethesda IV–VI) require surgical resection for nal diagnosis
(Table 80.2).
Other Imaging Techniques
Computed tomography (CT) and magnetic resonance imaging (MRI) are used in conjunction with US assessment for the evaluation of substernal components in large goiters and for
staging of thyroid malignancy. Positron emission tomography (PET) also has been used to
localise thyroid cancer recurrence when TG levels are high with inconclusive CT scans, but
its overall sensitivity and specicity are low.
Table 80.2 Cytological classications of ne-needle aspirates and the corresponding management
Diagnostic category
Cytological diagnosis ManagementThy classication Bethesda system
Thy1 I Nondiagnostic US assessment ± repeat
FNA
Thy2 II Benign Correlate with US and
clinical ndings
Thy3 III Neoplasia/atypia possible
Thy3a—atypia
Thy3f—atypia (possible
follicular neoplasm)
Thy4 IV–V Suspicious of malignancy Diagnostic
Thy5 VI Diagnostic of malignancy Total thyroidectomy
KEY POINTS
• Thyroid disorders are divided into functional and structural abnormalities.
• A nodule is the commonest presentation of thyroid malignancy.
• Normal TSH rules out thyroid dysfunction.
• The presence of TSH-receptor antibodies and thyrotoxicosis is diagnostic of Graves’
disease.
• US ± FNAC is the investigation of choice of initial assessment of structural thyroid lesions.
414 Head and Neck Endocrine Surgery
Repeat US-guided FNAC
Diagnostic
hemithyroidectomy
hemithyroidectomy
BENIGN THYROID DISEASE
81. BENIGN THYROID DISEASE
Introduction
Benign thyroid disease encompasses abnormal enlargement of the thyroid gland, thyroid
hormone imbalance, and thyroid tenderness.
Hyperthyroidism
Hyperthyroidism is diagnosed by suppressed levels of thyroid-stimulating hormone (TSH)
and increased thyroxine (T4)/triiodothyronine (T3). yrotoxicosis is driven by β-adrenergic
overactivity and the intracellular action of thyroid hormone. Hyperthyroidism is ten times
more common in females than in males, and the incidence increases with age. T3 toxicosis
accounts for 10% of thyrotoxicosis. e signs and symptoms of hyperthyroidism are shown
in Table 81.1.
Graves’ Disease
Graves’ disease is the commonest cause of thyrotoxicosis in iodine-replete regions of the
world. It is ve times more common in females than in males, with a peak incidence in the
twenties and thirties. It is characterised by a syndrome of hyperthyroidism, diuse goitre,
ophthalmopathy, and dermopathy. e pathogenesis is an autoimmune condition with IgG
autoantibodies targeting TSH receptors (TRAb) and stimulating thyroid hormone synthesis and secretion. Increased expression of broblast growth factor, found in the majority of
patients, leads to a diuse goiter.
Onset of symptoms is usually gradual and insidious. Ophthalmopathy is found in half of
patients and is due to swelling of the extraocular muscles, proliferation of periorbital fat, and
muscle brosis leading to muscle tethering. Smoking doubles the risk of ophthalmopathy.
Exophthalmos and eyelid retraction are common clinical ndings, and in severe cases, corneal ulceration may develop.
Diagnosis is made in the hyperthyroid patient by measuring TRAb. Management is categorised into medical, radioiodine, and surgical options. Graves’ disease is rarely self-limiting.
Antithyroid drugs are rst-line medical management and are tried for 12–18 months, with a
third of patients achieving lasting remission. Poor prognostic factors for relapse in patients
treated medically initially are shown in Table 81.2.
Table 81.1 Signs and symptoms of hyperthyroidism
Symptoms Signs
Weight loss Sinus tachycardia
Anxiety Atrial brillation
Agitation Fine tremor
Irritability Warm, moist skin
Palpitation Palmar erythema
Fatigue and weakness Onycholysis
Breathlessness Hair loss
Heat intolerance Proximal myopathy
Sweating Muscle wasting
Increased appetite High-output heart failure
Menstrual irregularity Thyroid bruit
Hair loss
Brittle nails
Head and Neck Endocrine Surgery 415
BENIGN THYROID DISEASE
Table 81.2 Poor prognostic factors for relapse of medically treated
Graves’ disease
Factor type Prognostic factor
Demographic Male sex
Age <40 years
Clinical history Repeated episodes of relapse
Presence of a large goitre
Biochemical Severe biochemical disease
Greatly increased T3:T4 ratio
High levels of TSH receptor antibodies
Radioiodine can exacerbate eye symptoms and is relatively contraindicated in patients with
ophthalmopathy (steroid cover required), and it is absolutely contraindicated in pregnancy
and breast-feeding. A total thyroidectomy oers cure with a low recurrence rate.
Toxic Multinodular Goitre
Toxic multinodular goitre is the most common cause of hyperthyroidism in the elderly
in iodine-decient regions. Atrial brillation is the principal sign. Denitive treatment is
with radioiodine, resulting in permanent hypothyroidism in most patients. Surgery (total
thyroidectomy/thyroid lobectomy) is reserved for patients with compressive symptoms,
patients with large goitre and cosmetic concerns, or patients with contraindications to
radioiodine.
Solitary Toxic Adenoma
Solitary toxic adenoma is a benign tumour that autonomously secretes thyroid hormone
and that results from TSH receptor activation. It occurs commonly in the fourth and
h decades and is an uncommon cause of thyrotoxicosis (5%). Many patients have a
palpable nodule, although the autonomously functional thyroid tissue can be diuse.
Radionuclide scanning dierentiates a solitary toxic adenoma from other causes by demonstrating a focus of isotope accumulation, a ‘hot spot’. Radioiodine treatment is ideal
because radioiodine is preferentially taken up in the hyperfunctioning nodule, sparing
the rest of the gland.
Destructive Thyroiditis
Destructive thyroiditis is an inammatory condition of the thyroid and is categorised into
conditions that are painful and those that are not (Table 81.3).
Treatment of Thyrotoxicosis
Treatment strategies for thyrotoxicosis are categorised into medical, nuclear medicine,
and surgical approaches. Medical management entails antithyroid drugs ± beta blockers.
ionamines are prescribed in a ‘block and replace’ or titration regimen. e most common
side-eect is pruritic rash. e most serious side-eects are agranulocytosis and liver failure.
Lugol’s iodine solution is variably used as a second-line control in the work-up for surgery.
Radioiodine is safe and eective and is considered rst-line treatment in the elderly and
those with cardiac dysfunction who may not tolerate physiological stress of surgery. Surgery
is the preferred option in toxic multinodular goitre, in those with compressive symptoms,
and in Graves’ disease associated with eye disease.
Pre-Operative Preparation of Hyperthyroid Patients
yroid surgery can result in the liberation of preformed thyroid hormone, precipitating
‘thyroid storm’, which has a mortality of up to 50%. Avoidance by pre-operative preparation
is paramount and involves antithyroid drugs to restore euthyroidism, beta-adrenergic blockade, and Lugol’s iodine, which can reduce the vascularity of the thyroid.
416 Head and Neck Endocrine Surgery
BENIGN THYROID DISEASE
Hypothyroidism
Hypothyroiidism is insucient production and secretion of thyroid hormones. It aects
females more frequently than males, with a peak incidence in the forties and ies. e most
common cause in iodine-replete regions is Hashimoto’s thyroiditis, and iodine deciency in
nonreplete regions. Myxedema refers to accumulation of glycosaminoglycans in the dermis
in the context of severe hypothyroidism. It is most easily identied in the lower leg, as pretibial myxedema.
e clinical eects of hypothyroidism can be categorised into generalised slowing of metabolic processes and an accumulation of glycosaminoglycans. e diagnosis is made by low
serum T4 concentrations in the presence of normal levels of TSH.
Management entails returning the patient to a euthyroid state clinically and biochemically
with levothyroxine replacement.
Hashimoto’s Thyroiditis (Chronic Autoimmune Hypothyroidism)
Hashimoto’s thyroiditis is characterised by diuse lymphocytic inltration of the thyroid
gland in the presence of circulating anti-TPO antibodies causing follicular destruction and
brosis. Patients may have subclinical hypothyroidism at initiation but progress to hypothyroidism over the years.
Thyroid Disease in Pregnancy
Hyperthyroidism
yroid disease in pregnancy is associated with adverse outcomes; therefore, a euthyroid
state is required throughout pregnancy to limit developmental risk to the fetus. High
levels of HCG in pregnancy can cause a transient hyperthyroidism by stimulating TSH
receptors.
In Graves’ disease, untreated hyperthyroidism is associated with miscarriage, premature
labor, low birthweight, and pre-eclampsia. erefore, an endocrinologist, an obstetrician,
and a pediatrician should jointly manage these patients. Management entails rapid return to
a euthyroid state and symptom control. Propylthiouracil is the preferred antithyroid agent in
the rst trimester because it has fewer teratogenic eects; however, carbimazole is preferred
in the second and third trimesters due to its causing fewer liver function abnormalities. At
20 weeks, TSH-receptor antibody concentrations should be measured, and patients with signicantly raised levels should be closely monitored due to transplacental transfer leading to
fetal thyrotoxicosis.
Hypothyroidism
Hypothyroidism is rare in early pregnancy and is associated with increased risk of spontaneous miscarriage, pregnancy-induced hypertension, pre-eclampsia, low birthweight, and
perinatal mortality. Treatment entails preventing hypothyroidism, doubling thyroxine dose
2 days of the week in early pregnancy, and monitoring TSH in each trimester. Iron supplementation and antacids, commonly prescribed in pregnancy, may aect thyroxine absorption. Due to the signicant risk of pre-eclampsia, prophylactic aspirin is advised.
Euthyroid Goitre
A goitre may be diuse or result from the presence of one or multiple nodules. e lifetime
risk of developing a thyroid nodule is 5–10%. e enlargement may be due to physiological factors (puberty and pregnancy), metabolic factors (endemic goitre), abnormal iodine
metabolism, or inammatory (Hashimoto’s)/autoimmune disease (Graves’ disease). e causes
of thyroid nodular enlargement are listed in Table 81.4.
Most goitres are asymptomatic. However, mechanical compression of the trachea and/or the
oesophagus may occur. Patients may notice a change in their shirt collar size or they may stop
wearing necklaces.
Head and Neck Endocrine Surgery 417
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