Thyroid
disorders
Goitre
An
enlargement in the thyroid gland seen as a swelling in the neck.
Occasionally it may press on a vital structure in the neck such as a vein or
one of the nerves which controls the vocal cords in the larynx.
Simple Goitre is the most
common type, occurs in highland areas away from the sea such as
Lack of Iodine in the diet,
it is now added to salt. Also found in milk, eggs, sea fish and crops grown
near the sea.
May be treated clinically
with potassium iodine 100 mg orally/day.
Hyperthyroidism or
thyrotoxicosis
Over production of thyroid
hormone, (T4) or tri-iodothyronine, (T3)
Eight times more common in
females
Often appears between 15 - 30
years of age
Clinical Features
Over-production
of thyroxine.
All the cells of the body are
metabolically stimulated
Nervous, anxious and easily
upset
Tachycardia
Increased heat production
Increased respiration
Moist, warm flushed skin
Vasodilation and tachycardia
continues in sleep, (unlike anxiety)
Weight loss
Often a moderate smooth
goitre
Possible increased frequency
of bowel activity.
Protrusion
of the eyeballs.
Oligomenorrhoea
The combination of
hyperthyroidism, goitre and exophthalmos is called
The cause of exophthalmos
seems to be the presence of a thyroid stimulating substance in the blood other
than TSH.
It may be LATS (Long acting
thyroid stimulator) or HTSI (Human thyroid stimulating immunoglobulin).
Complications
Atrial fibrillation Cardiac
failure Thyrotoxic
crisis
Treatment.
Antithyroid
drugs, radioiodine or surgical.
Thyroid tumours
May cause
up to 1 in 500 deaths in the
Benign - adenoma Malignant
- carcinoma
Most malignancies arise from
glandular tissue
Usually idiopathic, but may
be caused by radioactive iodine, was seen in Japanese nuclear explosion
survivors.
In hyperthyroid patients with
tumour they can be diagnosed by looking for "hot nodules" using a
radio iodine label.
However most thyroid tumours
do not show physiological activity, (ie. are non-toxic as opposed to a toxic
adenoma).
May exert pressure on vital
neck structures
Spread first to neck lymph
nodes and later by lymphatics and the bloodstream.
Treatment is by surgical
excision.
Hypothyroidism.
A deficiency
in thyroxine levels.
In adults this causes
myxoedema.
In children it causes
cretinism
Cretinism
Thyroid function is essential
to normal growth and development.
A cretin is a mental and
physical dwarf.
Classically
occurred in highland areas away from the sea.
Tadpoles also fail to develop
into frogs if deprived of iodine.
A few occasional cases may be
due to a congenital disorder of the thyroid gland.
As is usual in developmental
abnormalities treatment must be started early, later treatment will not allow
the individual to catch up.
Myxoedema
Hypothyroidism
which develops after maturation.
Most common in middle aged
women.
Clinical Features
All mental and physical
processes are slow.
Skin is puffy.
Slow speech and pulse.
Patients feel cold and may
sit for hours by the fire.
Blood cholesterol is raised
and atherosclerosis will develop.
The glandular tissue of the
thyroid gland is progressively destroyed, possibly by an auto-immune reaction.
Fibrous scar tissue develops.
Auto-immune thyroid disease
is termed Hashimoto`s disease.
Thyroid -
Surgical aspects
Anatomy
Situated just below the
larynx on tow sides of the trachea
Gland is highly vascular
Arterial supply - superior
and inferior thyroid arteries
Venous drainage - superior,
middle and inferior thyroid veins
Recurrent laryngeal nerves
lie posterior to the gland, these supply many of the
laryngeal muscles so are important for voice production and airway maintenance
Gland
products
Thyroxine T4 Triiodothyronine
T3
Both T3 and T4 are stored as
thyroglobulin in thyroid follicles prior to release
Stimulates oxygen consumption
Regulation of fat and
carbohydrate metabolism
Normal growth and development
Normal lactation
Parafollicular cells secret
calcitonin
Calcitonin is produced in
response to increased blood calcium
Calcitonin increases
excretion of calcium in urine and transfers calcium into bone
Four parathyroid glands are
attached to the posterior surface of the thyroid gland and secrete parathormone
Parathormone increases
absorption of calcium from the gut, moves calcium from the bones into the
tissue fluids and decreases renal excretion.
Undersecretion of
parathormone therefore leads to low serum calcium which causes tetany (muscle
spasms)
Hyperthyroidism
8:1 female:male
Grave`s disease
Most common form of
hyperthyroidism
Gland is diffusely enlarged -
smooth toxic goitre
Exopthalmic goitre
Autoimmune
IgG antibodies bind to
thyroid TSH receptors mimicking the effect of TSH
50% concordance in MZ twins
Nodular toxic goitre
May be multiple or solitary -
multiple most common Patient
may be euthyroid or hyperthyroid
May cause laryngeal nerve
palsy May
compress oesophagus or trachea
Tumours are the other main
indication for thyroidectomy
Pre op
Normally do not have
prophylactic anticoagulants ECG
Bloods Base
line obs
CXR Assess
vocal cords
Procedures
Thyroid lobectomy - removal
of one lobe for a nodular tumour
Subtotal thyroidectomy -
about five sixths of the gland are removed leaving the posterior portions of
each lobe intact. This preserves the parathyroid glands and protects the
recurrent laryngeal nerves.
Total thyroidectomy - removal
of both lobes and the isthmus, usually for bilateral carcinoma
Post op
complications
Airway problems
Damage to trachea Laryngospasm
secondary to tracheal irritation
Neck pain may prevent
effective expectoration
Recurrent laryngeal nerve damage
Can cause laryngeal paralysis
leading to respiratory difficulties - emergency tracheostomy may be required
Hoarseness a common symptom
Haemorrhage
Haematoma may arise in the
neck - neck sutures/stapes may need to be removed to allow haematoma to expand.
Surgical evacuation may be
required
Thyroid crises
Sudden surge of thyroid
hormone release due to handling the gland
Peak time 6 -24 hours post op Shortness
of breath
Hot Palpitations
Confusion/mania Tachycardia
hypertension
Treatment of crisis
Oxygen Sedation
Correct dehydration and
hyperthermia IV
beta blockers
Antithyroid drugs eg. carbimazole Corticosteriods
Tetany
Damage or loss of
parathyroids will lead to a decrease in serum calcium
Hypoparathyroidism causes
hypocalcaemia
Tetany develops in the early
days post op
Numbness and tingling in
fingers and toes Carpopedal
spasm
Spasm in facial muscles Voice
changes due to spasm of vocal cords
Treatment of tetany
IV calcium gluconate then
oral calcium supplements
Notes
The thyroid gland belongs to the
Endocrine system. The thyroid gland
is situated in the neck just below the larynx. It is highly vascular.
Weighs 20-30 g - has a high rate of blood flow per gram of tissue-130mls/min.
Two lobes linked by an isthmus, crosses front of trachea. There are 4 parathyroid
glands which lie in pairs on the posterior aspect. They
secrete parathormone which affects calcium metabolism. Calcitonin is produced
by other cells in the thyroid gland and has a role in reducing calcium
concentration in body fluids.
The thyroid lies near the airway, is highly vascular,
shares innervation from the nervous system with the vocal cords
Role of the thyroid gland
The follicular cells produce
the main thyroid hormones triiodothyronine (T3) and thyroxine (T4). Iodine is essential from the diet to
allow synthesis of the thyroid hormones and is obtained from sea food, vegetables
grown in soil with iodide, iodized salt.
The hormones from the thyroid are released into the general circulation by
the blood to all tissues where they act as a catalyst hastening oxidation
processes in the tissue cells. Thyroid hormone levels are controlled by
Negative Feedback involving the hypothalamus and anterior pituitary gland.
The primary function of the
thyroid hormones is to control the cellular metabolic activity. They act as a general pacemaker by
accelerating metabolic processes.
Through their widespread effects on cellular metabolism they influence every
major organ system.
Regulating the basal
metabolic rate (BMR)
Normal growth and development
Potentiation of the action of
other hormones
More specifically the thyroid
hormones have 2 major physioligic effects.
They increase protein
synthesis in virtually every body tissue (the exact mechanism has not been
precisely defined)
They increase oxygen
consumption by increasing the activity of the sodium/potassium ATPase (Na pump), primarily in tissues responsible for
basal oxygen consumption (i.e. liver, kidney, heart and skeletal muscle)
EUTHYROID -
hormones
produced at normal level
GOITRE - any
enlargement of the thyroid gland
HYPOTHYROID - underactivity of the thyroid gland
HYPERTHYROID - overactivity of the thyroid gland
HYPOTHYROIDISM (Adult) or Myxoedema is caused by a
variety of conditions
1. Causes and predisposing
factors
Usually affects middle-aged
and elderly women.
Slow progression of thyroid hypofunction, followed by symptoms indicating thyroid
failure. More than 95% have primary
dysfunction of the thyroid gland itself
Primary -
may
be atrophy of secretory cells
Secondary - inadequate
stimulation from the anterior pituitary
The most common cause of
hypothyroidism in adults is autoimmune thyroiditis or
Hashimoto's thyroiditis which is marked by goitre and myxoedema
Hypothyroidism may occur
after extensive thyroid surgery
2. Associated pathophysiological changes
Insufficient hormonal secretion released into the
bloodstream
\/
Rate at which the cells use energy is reduced
\/
Basal metabolic rate falls
\/
Less energy is produced
\/
Body temperature falls
\/
Energy Stores increase
3. Common clinical features of the disorder
Slowing up of all body
processes
Weight increases
Gut movements sluggish-->
constipation
Heart, respiration and blood
pressure reduced
Thought processes slow
down-->lethargy--apathy
Skin-->thick, leathery-->puffy
Hair-->brittle, sparse,
dry
The patient with advanced myxoedema is hypothermic and abnormally sensitive to
sedatives, opiates and anaesthetic agents.
Therefore caution is required in administration.
What might be the treatment?
Uncomplicated cases -
thyroxine orally, small dose to start
gradually increase
to prevent rapid acceleration of metabolism and affect on heart.
Overdose-->palpitations,
restlessness, hyperactivity, nervousness, insomnia
Maintenance dose individual,
continue indefinitely.
Nursing care symptomatic
Severe cases, may cause coma and hypothermia
Problems in the elderly.
Detection - Why?
Problems of treatment
Angina (myxoedema
leads to atherosclerosis)
Elderly arteriosclerotic
patients may become confused as the Metabolic Rate is increased too quickly
Thyroid hormones can affect
glucose levels, which can affect insulin needs
Interacts with many other
drugs- -SEE
BNF
Hyperthyroidism or thyrotoxicosis
Overactivity - excess
secretion of thyroid hormones
1. Causes and predisposing factors
Affects females more than
males
Simple overactivity of the gland
Hormone-secreting
benign tumour
Carcinoma
of the thyroid gland
Graves'
disease or primary thyrotoxicosis is the single most
common cause of hyperthyroidism.
An autoimmune disorder
Eight times more common in
women
Age - usually between 20-40
years
Familial tendency
There is a toxic enlargement
and inflammation of the thyroid with deposition of immunoglobulins and serum
proteins, which stimulate inflammation.
The exact cause of the disease is not known, but it involves the
formation of autoantibodies to TSH. More complex immunoglobulin reactions
lead to excessive production of the thyroid hormones. The main features of Graves' disease are
central nervous system disturbances and there may be exophthalmos.
2. Associated Pathophysiological changes
Excess Hormones are distributed via the blood
\/
Speeds up oxidation in the cells
i.e. rate at which the cell uses energy
\/
Basal metabolic rate is raised
By product of increased cellular activity is more heat
produced
\/
Rise in Body Temperature
\/
Profuse Sweating
\/
Energy stores depleted
\/
Speeding up of all body processes
3. Common clinical features of the disorder
Nutrition and metabolism
Appetite increases but weight
falls, muscle wasting
Increase heat intolerance
Sometimes impaired glucose
tolerance - glycosuria
Altered elimination
Movements of GI tract
increased-->Diarrhoea, nausea, vomiting
Altered CVS activity
Increase in Heart rate,
tachycardia, palpitaions, atrial fibrillation
Increased cardiac output
Increased blood pressure
Older patients may present
with congestive cardiac failure
Altered respiratory activity
Increased respirations, may
be shortness of breath
Altered activity patterns, mental and emotional status
Muscular tremor and
nervousness are marked
Weaknness and
fatigue
Become excitable, irritable
apprehensive
Insomnia
Altered skin integrity
Skin warm and increased
sweating
Altered patterns of sexuality
Impact of exophthalmus
and goitre on body image
Menstrual disorders (oligomenorrhoea, amenorrhoea)
Care is symptomatic
Propanalol is used to
provide rapid relief from some of the major effects of thyrotoxicosis.
This is contraindicated if the patient has suspected myocardial dysfunction as
it may cause heart failure.
Treatment:
1. Drug therapy -anti-thyroid drugs
that interfere with the synthesis of thyroid
hormones
2. Radioactive iodine -
for destructive effects on the thyroid
3. Surgery - where most of the thyroid is removed
The course of the disease may
be mild, characterised by remissions and exacerbations, and terminating with
spontaneous recovery in the course of a few months or years. Or progress may be relentless, with the
untreated person becoming emaciated, intensely nervous, delirious, even
disorientated, and the heart eventually fails.
Thyroid neoplasm’s are
either benign or malignant.
Benign thyroid adenomas which are encapsulated are
common.
Thyroid carcinomas are rare, accounting for only 1% of
malignancies (Leight, 1991)