Transcript Thyroid Gland

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Thyroid Gland
 The metabolism of Virtually all nucleated
cells of many tissues in the body is controlled
by thyroid hormone
 Over activity (Hyperthyroidism) and under
activity (Hypothyroidism) of the gland are
most common of all endocrine problems
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Thyroid Gland
 Anatomy:
It has two lateral lobes connected by
Isthmus
 It moves on swallowing as it is attached to
thyroid cartilage and trachea
 Embryologically it originates from the base
of the tongue and then descends therefore
sometimes remnants of thyroid can be
found at the base of tongue (Lingual
thyroid)
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Thyroid Gland
 Anatomy:
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Thyroid gland has follicles lined by cuboidal
epithelial cells. Inside the follicle is colloid
(Iodinated glycoprotein Thyroglobulin) which is
synthesized by follicular cells.
Each follicle is surrounded by basement
membrane, between follicular cells there are
parafollicular cells containing calcitonin secreting
C cells
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Follicular & parafollicular cells
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Thyroid Gland
 Physiology:
 Thyroid gland synthesizes two hormones
 T3 – Triiodothyronin: acts at Cellular level
 T4 - L – Thyroxin: which is prehormone
 More T4 is produced than T3 in thyroid but
T4 is converted to T3 in periphery
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Thyroid Gland
Physiology:
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In Plasma more than 99% of T4 and T3 is bound
to protein (Thyroxin Binding Globulin TBG,
Thyroid Binding PreAlbumin TBPA) and Albumin
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Thyroid Gland
Physiology:
Control of hypothalamic–pituitary–thyroid axis:
Hypothalamus produces TRH – Thyrotropin
releasing hormone, it stimulates pituitary to
secrete TSH – Thyroid Stimulating Hormone.
 TSH stimulates activity of Thyroid Follicular
cells
 T3 & T4 are secreted in circulation by follicular
cells
 T3 & T4 has negative feedback effect on
Hypothalamus and pituitary
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Physiological
Effect of Thyroid
Hormone
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Thyroid Gland
 Thyroid Function Test:
 Free T4 Free T3 and TSH are available and
test can be done at anytime of the day
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Thyrotoxicosis
↓ TSH
Free T4 ↑
Free T3 ↑
T3 N or
Low
T3 N or
Low
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Primary Hypothyroidism
TSH ↑
Free T4 ↓
Or Low
Normal
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TSH Deficiency
(Pituitary)
↓ TSH
Free T4 ↓ or
Low Normal
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HYPOTHYROIDSM
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Hypothyroidism
 It is usually primary due to disease of
thyroid, but may be secondary to
hypothalamic – pituitary disease
(decreased TSH drive)
 It is more common in females
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Hypothyroidism
 Autoimmune Hypothyroidism
 It is most common cause and associated
with antithyroid antibodies
 It is six time more common in females
 It has association with other autoimmune
diseases e.g. pernicious anemia, Vitiligo etc.
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Hypothyroidism
 Hashimotos Thyroiditis
This is a form of autoimmune thyroiditis,
more common in females and occurs in late
middle age
 Causes atrophic changes and regeneration
leading to goiter formation
 TPO ( Thyroid per oxidase) antibodies are
present in high titer (> 1000 IU/L)
 Patient may be hypothyroid or Euthyroid,
though they may go through initial toxic phase
 Levothyroxin
is given when patient is
hypothyroid
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Hypothyroidism
 Post Partum Thyroiditis
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This is transient phenomena, observed after
pregnancy
It may cause Hyperthyroidism, Hypothyroidism
It is due to result of modifications to the immune
system in pregnancy
It is usually self limiting or leads to
hypothyroidism
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Defects of Thyroid Hormone Synthesis
 Iodine Deficiency
Iodine is required for synthesis of T3 & T4
 We take iodine in diet, if deficient than
people get goiter ( due to TSH stimulation)
 Patient may be euthyroid or hypothyroid
 Iodine deficiency is problem in many
countries e.g. Netherlands, India, Asia,
Africa, Russia
 Efforts
are made to prevent iodine
deficiency by adding iodine in common
salt.
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Defects of Thyroid Hormone Synthesis
 Dyshormonogenesis
Rare condition, due to genetic defect in the
synthesis of thyroid hormone
 Patient
develops hypothyroidism with
goiter
Note—Some people have Genetic defect
causing sensorineural deafness due to
mutation at chromosome 7, they have
goiter( hypothyroid) also and this condition
is called Pendred Syndrome
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Hypothyroidism Symptoms and Signs
*Bold type indicate important symptoms and signs
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Hypothyroidism
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Hypothyroidism
 Myxoedema:
 It
refers to Hypothyroidism plus
accumulation of mucopolysaccharide in
subcutaneous tissue
 Patient is slow, thick skin, dry hair, deep
voice, weight gain, cold intolerance,
bradycardia, constipation
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Hypothyroidism
Children with Hypothyroidism:
 Have slow growth velocity
 Have poor school
performance
Young Females with Hypothyroidism
 Hypothyroidism should be excluded in
all women with Oligomenorrhoea,
amenorrhoea, menorrhagia, infertility,
Hyperprolactinimia
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Hypothyroidism
 Investigations:
Serum Free T3, Free T4 and TSH
 High TSH confirms primary Hypothyroidism,
free T4 is low
 Other investigations:
 Anemia – usually normocytic normochromic
 But may be Macrocytic (due to associated
Pernicious anemia )
 Microcytic – in women due to menorrhagia
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Hypothyroidism
 Other Investigations:
 Increase serum creatinine Kinase –
with associated Myopathy
 Hypercholesterolemia and
hypertriglyceridaemia
 Hyponatremia – due to increase
ADH
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Hypothyroidism
 Treatment:
Thyroxin – T4 is given for life
 Dose 100 Micrgram daily for young patients
 50 microgram for small, old patient to be
increased to 100 microgram after 2 – 4 days
 If patient has IHD start with 25 Microgram daily
and increase dose at 3 – 4 week interval (
monitor by serial ECG)
 Aim of treatment is to restore T4 & TSH within
normal range
 Improvement on T4 takes 2 weeks or more and
resolution of symptoms takes about 6 months
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Hypothyroidism
 Treatment for Myxoedema:
 It
is severe hypothyroidism and patient
may present with confusion or even
COMA
 Myxoedema
Coma is very rare,
hypothermia is often present and patient
may have severe cardiac failure,
pericardial effusion, hypoventilation,
hypoglycemia, hyponatremia
 Mortality is high
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Hypothyroidism
 Treatment for Myxoedema:
T3 orally or IV 2.5-5 microgram 8 hourly
 O2
 Hydrocortisone 100 mg IV 8 Hourly
 Glucose infusion
 Gradual rewarming
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HYPERTHYROIDISM
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Hyperthyroidism
 Hyperthyroidism (Thyrotoxicosis) is common,
affecting 2-5% of all females
 Female-Male ratio 5:1
 Age 20-40 years
 More than 99% cases are caused by intrinsic thyroid
disease, pituitary cause is extremely rare
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Graves Disease
 This is most common cause of hyperthyroidism and is
due to autoimmune process
 IgG antibodies bind to TSH receptors in the thyroid
and stimulate thyroid hormone production (IgG
behaves like TSH)
 TSH receptor antibodies (TSHR – Ab antibodies) are
specific for Graves Disease
 Graves Disease is associated with autoimmune
disorders such as pernicious anemia, Vitiligo and
myasthenia gravis
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Other Causes of
Hyperthyroidism/Thyrotoxicosis
Solitary toxic adenoma/nodule
 It is cause of 5% cases of hyperthyroidism usually remit
after antithyroid drugs
Toxic multinodular goitre
 Commonly occurs in older woman
 Anti thyroid drugs control hyperthyroidism
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Other Causes of
Hyperthyroidism/Thyrotoxicosis
De Quervain’s thyroditis
 This is transient hyperthyroidism due to
inflammatory process, probably viral in origin
 There is fever, maliase, pain in the neck,
tachycardia and local thyroid tenderness
Thyroid function test show
- Hyperthyroidism
- Increased ESR
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Other Causes of
Hyperthyroidism/Thyrotoxicosis
De Quervain’s thyroditis
 Thyroid function test show (cont)
- Thyroid uptake show suppression of uptake in acute
phase due to follicular damage
- Hypothyroidism, usually transient, may follow after
few weeks
 Treatment of acute phase
- Aspirin
- Predinisolone
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Other Causes of
Hyperthyroidism/Thyrotoxicosis
Amiodarone – induced thyrotoxicosis (AIT)
 Amiodarone is anti arrhythmic drug – class 111 and
causes hyperthyroidism
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Symptoms and Signs of Hyperthyroidism
*Bold type indicate important symptoms and signs
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Clinical Features of Hyperthyroidism
The eye signs of lid lag and stare
 May occur with hyperthyroidism of any cause
Graves dermopathy
 Pretibial myxoedema – is in filtration of the skin on
the shin
 Thyroid Acropachy – very rare and consist of clubbing,
swollen fingers and periosteal new bone formation
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Clinical Features of Hyperthyroidism
(cont)
Atrial Fibrillation in the elderly
 Is frequent presentation
Children with hyperthyroidism
 May present – excessive height, hyperactivity
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Pretibial myxoedema
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Differential Diagnosis
 Anxiety (Sympathetic Stimulation)
There is tachycardia, tremor, but cold clammy hand
 In hyperthyroidism,
there is tachycardia ,tremor, warm hands, eye signs,
diffused goitre, weight loss despite increase appetide
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Hyperthyroidism Investigations
 Serum TSH is suppressed, free T4 or T3 are raised
 Thyroid per oxidase (TPO) and thyroglobulin
antibodies are present in most cases of Graves disease
 Thyroid stimulating immunoglobulin (TSI) are
present in Graves disease
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Hyperthyroidism
Treatment
 Three options are available
1. Anti thyroid drugs
2. Radio active iodine
3. Surgery
1. Anti thyroid drugs
 Carbimazole – 20-40mg/day 8 hourly or single dose
 Propylthioracial (PTU) – 100-200mg 8 hourly
 They inhibit the formation of thyroid hormones
 Propranolol (Beta Blocker) is used for symptomatic relief
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Hyperthyroidism
Treatment
Side effects of drugs
 Carbimazole – rash, nausea, vomiting, arthralgia,
agranulocytosis, jaundice
 PTU – rash, nausea, vomiting, agranulocytosis
NOTE – As agranulocytosis is the side effect, therefore,
patient is advised if he has sore throat, he should
report to hospital for investigation
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Hyperthyroidism
Treatment (cont)
2. Radioactive Iodine – 131Iodine
 Can be given to all patients
 Is contraindicated in pregnancy and during breast
feeding
3. Surgery
 Subtotal thyroidectomy/thyroidectamy
 Side effects – laryngeal nerve palsy occur in 1%
 Transient hypocalcemia up to 10%
 Permanent hypoparathyroidism < 1%
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Hyperthyroidism in Pregnancy
 During pregnancy Propylthioracial (PTU) is
preferred because there are reports of congenital
abnormalities with Carbimazole
 TSI – thyroid stimulating immunoglobulin cross
the placenta and stimulate fetal thyroid
 Carbimazole and PTU cross the placenta
 T4 (Thyroxin) very poorly crosses the placenta
 If necessary surgery can be performed in second
semester of the pregnancy
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Thank you
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