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PARATHYROID SURGERY
Inferior parathyroids can be found near or within the thyrothymic tract, which
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extends from the lower pole of the thyroid gland into the superior mediastinum.
e intersection of the inferior thyroid artery and the recurrent laryngeal nerve is a
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useful anatomical landmark.
Most parathyroid glands will lie within a 2.5-cm area either above or below this
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point.
Other locations are seen, with the inferior parathyroids having a wider distribution
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due to their longer descent. ese anatomical locations are discussed in detail below.
Bilateral Neck Exploration
With the introduction of imaging in parathyroid disease, there has been a shi towards more
minimally invasive approaches, but subsets of patients still require BNE, including those with:
Suspected multigland disease
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Parathyroid cancer
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Failed pre-operative localisation
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Failed MIP
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Current guidelines from the National Institute for Health and Care Excellence (NICE) on the
management of primary hyperparathyroidism (NG132) recommend that patients with negative or equivocal imaging (ultrasound and sestamibi scan—up to 20% of patients) should be
oered four-gland exploration and referral to a surgeon with expertise in BNE.
A failed minimally invasive approach will oen require a second operation for suspected
multigland disease or a double adenoma. Suspected multigland disease may occur in patients
with hyperplasia (up to 15% of patients with PHPT), double adenomas (4% of patients with
PHPT), or familial hyperparathyroidism, as in multiple endocrine neoplasia (MEN 1, MEN 2A),
familial isolated HPTH, and hyperparathyroidism-jaw tumour syndrome.
Technique
Ideally, patients give informed consent before the day of surgery. e procedure is normally performed under general anaesthesia. e patient is placed in a supine position with
30 degrees of head elevation. e neck is extended using a sandbag placed under the shoulders, with the head stabilised on a head ring. Local anaesthetic with or without epinephrine
may be inltrated as a supercial cervical block or directly into the site of the incision. A
5-cm curvilinear incision is placed 1–2 cm above the sternal notch. A subplatysmal ap is
raised superiorly to a point just above the cricoid cartilage. e strap muscles are then separated in the bloodless midline plane. Haemostasis is important, because blood in the surgical
eld can make visualisation of the parathyroid glands dicult.
e le or right side of the neck is opened by raising the strap muscles o the thyroid, with
lateral retraction of the carotid sheath and medial retraction of the thyroid. is manoeuvre
ensures that the area directly surrounding the dorsal thyroid and tracheo-oesophageal gutter may be explored.
e thyroid lobe is rotated medially into the wound to allow inspection of the posterior
aspect (Figure 89.1).
e search should proceed in a methodical way. Ideally, no gland should be removed until
all have been visualised.
Superior glands are more constant in position and generally lie on the posterior surface of the
thyroid gland, within 1 cm of the cricothyroid joint, posterior to the recurrent laryngeal nerve.
Enlarged superior glands oen migrate downward and inferiorly into a retropharyn-
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geal/retro-oesophageal position by the combined eects of gravity and swallowing.
Superior glands can be found by identifying the inferior thyroid artery laterally and
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the recurrent laryngeal nerve inferomedially and by entering the retropharyngeal
space by delicate dissection.
448 Head and Neck Endocrine Surgery
PARATHYROID SURGERY
Figure 89.1 The inverted relationship between the left superior parathyroid (PA) and the left
recurrent laryngeal nerve (RLN) when the left thyroid lobe is retracted onto the trachea.
e inferior thyroid gland is found near or within the thyrothymic tract, which extends from
the inferior pole of the thyroid gland into the superior mediastinum, usually anterior to the
recurrent laryngeal nerve.
Dissection into the thyrothymic tract will usually identify the gland.
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An inferior parathyroid gland can sometimes lie within the thymus and its delivery
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should only be performed if an adenoma is not found on either side of the neck, to
avoid devascularising a normal but suppressed gland.
ymic delivery is facilitated by dissection inferiorly, anterior to the carotid artery but
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medial to the recurrent nerve and lateral to the trachea at the level of the clavicle. e
thymus continues as an extension of the thyrothymic tract, and progressive traction
on its capsule will aid delivery from the chest (Figu re 89.2).
If a superior parathyroid gland is not found, exploration of the retropharyngeal/retrooesophageal compartment and posteromedial surface of the superior thyroid pole is
Figure 89.2 Left thymic remnant being delivered from the mediastinum and containing an
ectopic inferior parathyroid adenoma.
Head and Neck Endocrine Surgery 449
PARATHYROID SURGERY
BOX 89.1 CONTRAINDICATIONS TO MIP
• Negative imaging
• Multigland disease
• Family history of MEN or familial hyperparathyroidism
• Chronic renal insufciency
• Hyperparathyroidism from lithium therapy
• Suspected parathyroid cancer
warranted; then, inspection behind the hyoid and larynx and within the carotid sheath at
the level of the inferior thyroid artery is performed.
If an inferior parathyroid is not identied, the carotid sheath is explored from the level of the
superior thyroid artery down to the sternoclavicular joint.
One should remember the law of symmetry in parathyroid surgery:
In 80% of cases, a parathyroid gland located on one side of the neck will have a corresponding gland in the same location on the other side.
If, aer a meticulous search, no abnormal parathyroid glands are identied, then one should
reconsider the diagnosis and carefully document the location of identied glands. If abnormal or suspect parathyroid glands are identied, then frozen section and ioPTH are useful
adjuncts to decision-making.
Minimally Invasive Parathyroidectomy
e MIP approach to the parathyroid glands is facilitated by accurate pre-operative localisation via scans. See Endocrine imaging (Chapter 79). Contraindications to MIP are listed in
Box 89.1.
Technique
e patient is positioned similarly to positioning for BNE. e procedure can be performed
under local or general anaesthesia. e initial incision can be either a medial or a focused
lateral approach.
Lateral Approach
Incision is made in the medial border of the sternocleidomastoid muscle (SCM) over
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the pre-localised adenoma.
e incision is deepened and a subplatysmal plane is developed.
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e medial border of the SCM is identied and a plane is developed.
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Lateral retraction of the SCM and jugular vein with medial traction on the strap mus-
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cles allows the thyroid gland to be identied.
ese simple manoeuvres allow most pre-localised parathyroid adenomas to be
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identied.
Medial Approach is Like the Approach for BNE
is approach also allows identication of the other parathyroid gland to ensure they
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both are normal.
Wounds are closed with absorbable sutures in the strap muscles/platysma and Monocryl
sutures for the skin.
Complications
Complications are rare following parathyroid surgery and are listed below in Box 89.2.
450 Head and Neck Endocrine Surger y
MEDICOLEGAL ASPECTS OF THYROID AND PARATHYROID SURGERY
BOX 89.2 COMPLICATIONS OF PARATHYROIDECTOMY
• Bleeding
• Wound infection
• Recurrent laryngeal nerve palsy (<1%)
• Hypoparathyroidism (rare and more common in BNE)
• Failure to cure (2–5%)
KEY POINTS
• Surgery provides the only cure for patients with primary hyperparathyroidism (PHPT).
• Bilateral neck exploration is reserved for patients with suspected multigland disease,
patients with negative imaging, or those undergoing revision surgery.
• Knowledge of embryology and anatomy is important to ensure successful
identication of parathyroid glands.
• The intersection of the recurrent laryngeal nerve and inferior thyroid artery is a key
landmark for identifying parathyroid glands.
• Enlarged superior parathyroid glands tend to migrate posteriorly and inferiorly while
inferior glands tend to migrate anteriorly.
• Intra-operative PTH assay and frozen section are useful adjuncts in parathyroid surgery.
Further Reading
Glaser SM, Mandish SF, Gill BS, Balasubramani GK, Clump DA, Beriwal S. Anaplastic thyroid
cancer: prognostic factors, patterns of care, and overall survival. Head Neck 2016;
38(Suppl 1): E2083–E2090. doi: 10.1002/hed.24384.
National Institute for Health and Care Excellence (NICE). Hyperparathyroidism (primary):
diagnosis, assessment and initial management. NICE guideline NG132, published
May 2019.
90. MEDICOLEGAL ASPECTS OF THYROID AND PARATHYROID SURGERY
Introduction
yroid and parathyroid operations oer unique challenges that are reected in the complications and litigation that can arise. Surger y-related lega l claims (see Box 90.1) have decreased
since 2011—with ENT representing about 2.5% of claims—and a higher proportion are being
defended. irteen to fourteen claims per year pertain to thyroid disease.
44% of claims are resolved without payment.
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<5% of all cases are decided in court.
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79% of court cases are successfully defended.
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Diagnosis
Delayed and incorrect diagnosis cause approximately one third of all thyroid-related claims
in the United Kingdom. Internationally, 6–8% of cancer-related claims and 6% of all thyroidrelated claims arise from delayed diagnosis, with the requirement for a second operation
increasing the chance of a successful claim.
Head and Neck Endocrine Surgery 451
MEDICOLEGAL ASPECTS OF THYROID AND PARATHYROID SURGERY
BOX 90.1 THE LEGAL DEFINITION OF MEDICAL NEGLIGENCE
A successful claim of medical negligence must prove:
• Breach of duty of care: Treatment below the reasonable/accepted standard
• Damage: Patient injury or loss
• Causation: The injury would not have occurred or would have been less severe with
appropriate treatment
The claim must be brought within a specic period of limitation. Successful damages
awards reect two elements:
• Pain, suffering and ‘loss of amenity’ (i.e. nonnancial impact)
• Financial loss and extra expenses
NHS Resolution (formerly called the NHS Litigation authority) manages NHS-related claims.
False-negative thyroid ne-needle aspiration (FNA) rates are <3–10.2%, and suspicious features on ultrasound are reported in 90% of patients with false-negative FNA.
Inadequate or incongruous cytology indicates repeat FNA.
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Evidence on the eect of delayed thyroid cancer diagnosis is limited. A small Korean
study found mortality was lowest for patients who had thyroid surgery 1–4 weeks aer
diagnosis but there was no increased risk with longer delays. An older retrospective
study found that cancer mortality was 4% in patients who underwent initial therapy
within a year, compared to 10% in others who waited longer. e ‘delayed’ group had
twice the 30-year cancer mortality (6% vs. 13%).
It is dicult to attribute negative outcomes to delayed diagnosis.
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Pre-operative thyroid function, calcium levels, and vitamin D status are predictive of
post-operative complications. Studies rarely separate these claims.
Guidelines recommend pre-operative biochemistry in at-risk patients.
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Pre-Operative Consent
Historically, a legal test (Bolam) determined whether the conduct of a doctor could be sup-
ported by a responsible body of U.K. medical opinion. e Sidaway judgement that followed
required doctors to decide how much risk information to disclose to patients. However, since
an early 2015 Supreme Court judgement (Montgomery v. Lanarkshire Health Board), doctors must now take ‘reasonable care to ensure that the patient is aware of any material risks
involved in any recommended treatment and of any reasonable alternative or variant treatments’. A material risk is one to which a reasonable person would be likely to attach signicance (i.e. a risk that might alter a decision).
e importance of adequate informed consent cannot be overstated, mainly for best patient
care and, secondly, for avoidance of undesired consequences if a claim of negligence is submitted. In the United States, 19% of vocal cord palsy, 7–9% of recurrent laryngeal nerve
injury, and 21% of spinal accessory nerve injury claims relate to consent.
Inadequate consent is a recognised major factor in legal claims being upheld.
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Unfortunately, patients have poor retention of consent information, and there is a
discrepancy between what surgeons and thyroid cancer patients feel is important.
In the United Kingdom, providing information whilst checking and facilitating
the patient’s understanding are overriding duties dened by the General Medical
Council and Royal College of Surgeons. Risk explanation should be tailored to
452 Head and Neck Endocrine Surgery
MEDICOLEGAL ASPECTS OF THYROID AND PARATHYROID SURGERY
patient-specic factors, such as thyrotoxicosis, age, previous surgery, and pre-existing
vocal cord palsy.
Patient information leaets (e.g. ENT UK website) are recommended but do not replace
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thorough discussion because they do not improve understanding.
Intra-Operative Factors
Experience of the Surgeon
High-volume thyroid surgeons have better outcomes. Despite variability in what constitutes
high volume, current evidence suggests that high volume means 35–40 thyroidectomies per
surgeon and 90–100 thyroidectomies per centre per year. is exceeds the British Association
of Endocrine and yroid Surgeons recommendation of 20 per year. However, it mirrors the
gures for paediatrics, where experience is thought particularly important.
Surgeons performing less than 30 relevant operations per year have approximately dou-
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ble the endocrine complications.
Recurrent Laryngeal Nerve (RLN) Injury
RLN palsy is the major motivator of surgery-related claims in U.K. thyroid surgery. Risk
factors include Graves’ disease, post-operative bleeding, retrosternal, malignant, recurrent
benign, malignant goitre and failure to identify the RLN.
Vocal cord movement should be documented pre-operatively.
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Due to the extremely high number of cases required to power a denitive study, it remains
uncertain whether intra-operative nerve monitoring (IONM) reduces RLN injury rates,
although for temporary RLN palsy, evidence seems to be amassing in favour of IONM.
It is imperative that IONM be carried out in the recommended manner, and failure to do
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so can expose surgeons to litigation.
Another IONM debate is whether bilateral thyroid surgery should be stopped and staged in
the event of loss of signal on the rst side. To settle this, surgeons and patients will need to
dene what is safe and acceptable. In the meantime, studies report that a staged approach
in the event of rst-side signal loss can eliminate occurrence of bilateral vocal cord palsy.
Regardless of approach, the local management algorithm should be pre-operatively discussed with patients.
Parathyroid Preservation
e preservation or removal of the correct parathyroid gland(s) is implicit to diligent surgery.
Recent American yroid Association (ATA) guidelines support the use of loupes and the
identication of at least two parathyroid glands.
Documentation
Documentation of relevant ndings, including the results of intra-operative investigations
that guided decision-making (e.g. parathyroid hormone biochemistry or frozen-section
pathology), should be completed.
e location and preservation of the RLN should be clearly documented on a legible
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(preferably typed) operation note that would stand up to scrutiny by an expert third
party in the event of a claim.
Post-Operative Factors
Post-operative ca re is as important as all other factors. Recent U.K. claim ana lysis showed eight
of een claims related to post-operative care were upheld. e issues in these cases included
hypocalcaemia management, diagnosis of vocal cord paresis, and haematoma development.
German experience suggests that claims are more likely to be successful if related to
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faulty post-operative care.
Head and Neck Endocrine Surgery 453
MEDICOLEGAL ASPECTS OF THYROID AND PARATHYROID SURGERY
Diagnosis of Vocal Cord Palsy
German and British guidelines recommend all thyroid patients have pre-and post-operative
laryngeal examinations. eir timing, although signicant in terms of detecting neuropraxia,
is not prescribed.
e failure to recognise a problem motivates 36% of U.S. vocal cord palsy-related claims
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(and 20% of spinal accessory-related claims).
Hypocalcaemia
Assessment of parathyroid function aer completion or total thyroidectomy is mandatory.
National specialist databases record post-operative hypocalcaemia rates of 21% aer total
thyroidectomy for multinodular goitre (MNG) and, in Scandinavia, 6.4% of patients required
intravenous calcium aer total thyroidectomy. Serum calcium or parathyroid hormone
biochemistry and routine calcium supplementation are all strategies to manage signicant
hypocalcaemia. Recommendations dier between North America and Europe regarding the
choice and timing of these tests.
ere is consensus that a robust protocol for management of post-operative hypocalcae-
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mia be in place.
Duration of Inpatient Stay
A patient’s attorney may question the safety of a <24-hr inpatient stay for a patient who
developed neck haematoma aer surgery. Risk factors for post-operative bleeding, which
occurs in 0.6–2.1% of cases, include re-operation and bilateral procedures. Although most
haemorrhages occur within 6 hours of surgery, 20–37% will occur aer 6–24 hours, and
0–10% aer 24 hours. Notably, the lowest serum calcium level can occur aer the second
post-operative day:
If discharged too soon, patients may develop severe, untreated hypocalcaemia.
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When Things Go Wrong
Since 2014, the U.K. duty of candour has placed a legal duty on care providers to inform
and to apologize to patients or their families regarding mistakes in care that led to death or
severe or moderate harm. is adds to a doctor’s ethical duty to disclose when an incident
has occurred.
Patients should be informed as soon as possible of any harm, with an apology and rel-
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evant reassurance provided.
A Claim Arises
Medical negligence cases that go to court are generally civil prosecutions. e plainti’s/
defendant’s attorneys will instruct an expert witness to provide a report on possible breach
of duty and/or condition and prognosis. An expert witness should provide an independent,
balanced opinion for the court (not the lawyers) on the facts of a case, an explanation of technical issues, a view on what is considered ‘reasonable’, and matters of causation (symptoms
or condition) that have arisen as a result of damage.
Litigation Rates and Costs
ree U.K. analyses including nearly 400 cases between 1971 and 2016 were analysed.
Diagnostic delay (40 cases, 51.4% closed claims successful), incorrect diagnosis (22 cases,
85% closed claims successful), and recurrent laryngeal nerve injury (33 claims, 54.5% closed
claims successful) robustly emerged as principal factors.
454 Head and Neck Endocrine Surgery
EVALUATION AND INVESTIGATION OF PITUITARY DISEASE
KEY POINTS
• Further investigate any discrepancies between ultrasound and cytology whilst aiming
to minimise diagnostic delay.
• Ensure that thyroid function and serum calcium are normal before and after surgery.
• Keep in mind the Montgomery v. Lanarkshire Health Board ruling when consenting
patients.
• Intraoperative nerve monitoring remains the subject of debate.
• At the very least, post-operative laryngoscopy should be performed in a patient with
post-operative voice symptoms.
• The defense of a medical negligence claim will depend upon your statement of:
• What you did—Were you the appropriate surgeon?
• Why you did it—What were the indications for surgery?
• What your notes say.
• How you managed the complication(s).
91. EVALUATION AND INVESTIGATION OF PITUITARY DISEASE
Introduction
e pituitary gland sits within the sella turcica of the sphenoid bone, inferior to the hypothalamus and optic chiasm. It is surgically accessible transnasally via the sphenoid sinus. e
gland is composed of two lobes. e anterior pituitary (adenohypophysis) secretes luteinising
hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), and prolactin. e posterior
pituitary (neurohypophysis) is not a gland in itself, but a projection of the hypothalamus, and
it releases antidiuretic hormone (ADH) and oxytocin. It is connected to the hypothalamus
above by the pituitary stalk (infundibulum), which passes through the diaphragm that forms
the roof of the sella. e function of the anterior pituitary is controlled chiey by hypothalamic hormonal control; the hypothalamic-pituitary-peripheral axis is regulated by multiple
feedback loops.
Clinical Features of Pituitary Disease
Pituitary disease may manifest clinically due to:
Hormone hyposecretion
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Hormone hypersecretion
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Mass eect
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Pituitary apoplexy
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A combination of the above
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Not all functionally signicant pituitary tumours are visible radiologically; conversely, incidental pituitary lesions are common.
Hormone Hyposecretion
One or multiple hormones may be reduced, leading to the clinical syndrome of
hypopituitarism. Deciency of GH is most common, leading to lethargy, decreased muscle
mass, central adiposity, and reduced bone density. LH and FSH hyposecretion results in
reproductive dy sfunction (low l ibido, infertil ity, erectile dysf unction in men, oli gomenorrho ea
Head and Neck Endocrine Surgery 455
EVALUATION AND INVESTIGATION OF PITUITARY DISEASE
in women, and delayed puberty in adolescents). ACTH hyposecretion leads to failure to produce an appropriate level of cortisol. is leads to lethargy, postural hypotension, and hyponatraemia when the person is under physiological stress (Addisonian crisis). Hypothyroidism
is less common but may manifest with typical symptoms of lethargy, dry skin, constipation,
etc. Hyposecretion of ADH from the posterior pituitary is rare, but it may lead to diabetes
insipidus (polyuria and polydipsia with hypernatraemia).
Hormone Hypersecretion
Hormone hypersecretion occurs due to the proliferation of secretory cells within an adenoma. e most common functioning pituitary adenoma is a prolactinoma, leading to low
libido, infertility, galactorrhoea in women, and gynaecomastia in men. Hypersecretion of
GH leads to acromegaly, with an insidious onset of tiredness, sweating, and bony and
so-tissue overgrowth. Hypersecretion of ACTH, and thus cortisol, leads to Cushing’s
disease, which includes central obesity, striae, diabetes, hypertension, cardiovascular disease, hirsutism, bruising, and proximal myopathy. Hypersecretion of TSH, FSH, or LH is
very rare.
Mass Effect
A pituitary macroadenoma may exert mass eect on surrounding structures. Pressure on
the optic chiasm due to suprasellar extension of the tumour initially leads to a bitemporal superior quadrantanopia, followed by bitemporal hemianopia. e visual eld defect
may be asymmetrical. e patient may be unaware of the visual eld defect or may complain of nonspecic symptoms, such as clumsiness. Less commonly, lateral expansion into
the cavernous sinus may lead to diplopia and ophthalmoplegia. Large pituitary adenomas
may cause headaches and rarely hydrocephalus due to obstruction of the third ventricle.
Headache is a common presenting symptom in pituitary disease but cannot always be
attributed to the tumour.
Pituitary Apoplexy
In a minority of patients, pituitary apoplexy can be the rst presentation of a pituitary adenoma. e classical presentation is severe, sudden headache and acute visual eld decit. e
patient may present with a triphasic abnormality of ADH secretion: initially, diabetes insipidus, followed by a period of a syndrome of inappropriate ADH secretion (SIADH), followed
by a return of diabetes insipidus.
Anterior Pituitary Function Testing
e presenting symptoms of a patient with a known sellar mass may guide the endocrine
investigations. Symptoms in many cases are nonspecic or non-existent. In such cases, the
laboratory tests are conducted to screen for either pituitary hormone hypersecretion or
hypopituitarism (Table 91.1).
Testing for Hypersecretion
Hyperprolactinemia is diagnosed with ba sal morning prolactin levels. Repeated tests or serial
cannulated prolactin levels are necessary to make the diagnosis condently, as levels can be
falsely elevated due to a stress response. Prolactin levels can be increased in hypothyroidism,
Table 91.1 Tests for pituitary hormone hypersecretion
Hormone Initial test(s) Conrmatory test(s)
Prolactin Morning serum prolactin level –
GH IGF-1 level Oral glucose suppression test
ACTH 24-hr urinary cortisol High-dose dexamethasone suppression test
TSH Serum free T4 and TSH Alpha-subunit levels
ADH Urine/serum Na & osmolalities —
456 Head and Neck Endocrine Surger y
EVALUATION AND INVESTIGATION OF PITUITARY DISEASE
in polycystic ovarian syndrome, with the use of some medications (e.g. metoclopramide
and some antidepressants), and with some nonfunctioning macroadenomas, due to stalk
compression.
Acromegaly (GH hypersecretion) is screened for by checking levels of insulin-like growth
factor (IGF-1), a downstream product of GH. e diagnosis is conrmed by a 75-g oral
glucose load that fails to suppress the GH level to <1 during the test.
Cushing’s disease (Cushing’s syndrome due to pituitary ACTH hypersecretion) can be challenging to diagnose, as many ACTH-secreting tumours are not visible on MRI. A detailed
endocrine workup is essential. Excess cortisol (hypercortisolism) must be demonstrated
rst, and subsequently, an adrenal or ectopic source of ACTH must be ruled out to conrm
a pituitary cause. As a screening test for hypercortisolism, 24-hour urinary cortisol is measured rst. Obesity, pregnancy, alcohol dependency, and poorly controlled diabetes should
be ruled out as potential physiological causes of high cortisol. Cushing’s disease is then conrmed by:
Dexamethasone suppression and measurement of serum ACTH. Failure of cortisol
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suppression to <50% aer dexamethasone suppression suggests Cushing’s. Plasma
ACTH levels will be elevated with a pituitary cause of Cushing’s but suppressed with
adrenal ACTH hypersecretion.
A reduction in serum cortisol aer high-dose dexamethasone administration favours
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a pituitary source over an ectopic one. Salivary cortisol can be measured instead of
serum cortisol.
Inferior petrosal sinus (IPS) sampling is used to conrm the source and lateralisation
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of excessive ACTH in pituitary Cushing’s. If the ACTH source is a pituitary adenoma,
samples from the IPS will demonstrate high ACTH levels, a dierential between IPS
and peripheral blood levels, and an exaggerated spike in ACTH levels following the
administration of corticotropin-releasing factor (CRF).
Elevated free T4 and TSH levels suggest the rare diagnosis of a TSH-secreting adenoma. High
alpha-subunit levels can be used to distinguish this from thyroid hormone resistance.
Testing for Hypopituitarism
Hypopituitarism is suggested where both the target hormone (e.g. T4) and the tropic hormone (e.g. TSH) are low. In most cases, dynamic testing is also required to prove that pituitary reserve is aected. Multiple dynamic tests can be performed simultaneously.
GH deciency and ACTH hyposecretion can be demonstrated by an inadequate response to
the insulin tolerance test or glucagon stimulation test. e glucagon stimulation test can be
performed when insulin is contraindicated (adrenal insuciency, coronary artery disease,
or seizure disorders). Basal LH, FSH, and sex hormone levels can be measured and are sufcient to establish the diagnosis of hypogonadism. e GnRH stimulation test is now rarely
used. yroid function tests (TSH, T4, T3) can conrm secondary hypothyroidism, and the
TRH test is generally not required.
Posterior Pituitary Function Testing
SIADH
Hyponatraemia has numerous causes and SIADH is an important one. SIADH is a diagnosis
of exclusion. SIADH can be conrmed with paired urine and serum sodium osmolalities.
Hyponatraemia demonstrated by reduced serum osmolality and associated with inappropriately high urinary sodium and osmolality conrms the diagnosis.
ADH Deciency—Diabetes Insipidus
ADH deciency leads to the production of large volumes of inappropriately dilute urine.
is results in compensatory polydipsia, urinary frequency, nocturia, and enuresis. A 24-hr
Head and Neck Endocrine Surgery 457
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