Thyroid and parathyroid glands

 INTRODUCTION
 ANATOMY
 DEVELOPMENT
 BRIEF HISTOLOGY
 REGULATION AND SECRETION OF THYROID
AND PARATHYROID HORMONES
Dr.Barkha.S.Tiwari 3

 CLASSIFICATION AND DISEASE OF
THYROID AND PARATHYROID GLANDS
 DENTAL CONSIDERATION
 CONCLUSION
 REFERENCES

 Endocrine glands??
They are ductless gland which releases their
hormone directly into the blood and play an important
role in homeostatis , eg: thyroid and parathyroid glands,
pituitary glands, adrenal glands, pancreas and gonads.

 Endocrine hormones??
- released by glands or specialized cells into
the circulating blood and influence the function of cells
at another location in the body.

 Anterior surface of trachea just
inferior to thyroid cartilage (or
Adam’s apple)
 Two lobes- right and left
connected by isthmus
 Gland weighs about 25g
 Larger in females than in males
Thyroid gland
(shield like)

The only endocrine gland that is palpable and movable

• Usually paired.
• Very small (less than 5 mm).
• They are so called because they lie in close relationship to
the thyroid gland.
• Two glands are present one superior and one inferior on
either side, there being four glands in all.

 Located in the anterior
region of the neck
 This gland has an accessory
(pyramidal) lobe

Gland lies against vertebrae C5, C6 ,C7 and T1
Lobe extension is from middle of thyroid cartilage to
4th or 5th tracheal rings
Isthmus - 2nd to 3rd tracheal rings

It is the peripheral
condensation of the
connective tissue of
the gland
A dense capillary
plexus is present
deep to the true
capsule.
True
capsule It is derived from
the pretracheal
layer of the deep
cervical fascia
It forms a
suspensory
ligament on the
inner surface of the
gland connecting
the lobe to the
cricoid cartilage.
False
capsule

Lobes -conical shape having
Apex
Base
Surface - lateral, medial and
posterolateral
Borders - anterior and posterior

Lateral surface is convex covered by :
Sternothyroid, Sternohyhoid
Superior belly of omohyoid
Anterior belly of sternomastoidDr.Barkha.S.Tiwari 17

 Medial surface is
related to
 Trachea and oesophagus
(tubes)
 Inferior constrictor and
cricothyroid (muscles)
 External laryngeal and
recurrent laryngeal
(nerves)

Posterolateral surface related to
Carotid sheath and overlaps common carotid artery
Anterior border related to
Anterior branch of superior thyroid artery
Posterior border related to
Inferior thyroid artery
Anastomosis between superior and Inferior thyroid
artery
Parathyroid glands
Thoracic duct Dr.Barkha.S.Tiwari 19

 The thyroid gland and parathyroid glands are supplied by the
superior and inferior thyroid arteries.

 Superior thyroid artery- it is the first anterior branch of the
external carotid artery. It runs downwards and forwards in
intimate relation to the external laryngeal nerve.
 Inferior thyroid artery- it is a branch of thyrocervical trunk
which runs first upwards, then medially and finally
downwards to reach the lower pole of the gland

 The thyroid is drained by the superior, middle and inferior
thyroid veins.
Superior thyroid vein
emerges at the upper pole and
accompanies the superior
thyroid artery. It ends in the
internal jugular vein.
Middle thyroid vein emerges
medially and enters the internal
jugular vein.
Inferior thyroid veins emerge
at the lower border Dr.Barkha.S.Tiwari 22

 Upper part of gland -upper deep cervical lymph nodes
 Lower part of gland -lower deep cervical lymph nodes

Nerve supply
 Mainly - middle cervical ganglion (parathyroid gland)
 Partly -superior (parathyroid gland) and inferior cervical
ganglia
 These are vasoconstrictor

They develop from the
pharyngeal arches which are
the mesodermal thickenings
in the wall of the cranial-
most part of the foregut.

The parathyroid glands are
derived from the third and
fourth pharyngeal pouch.

The midline swelling present between the two mandibular
arches are called the tubercular impar.

The site of origin is called the foramen caecum.
The tubercular impar is soon depressed below the surface to form a
diverticulum called the thyroglossal duct.
The diverticulum goes down and its tip bifurcates.
The proliferation of the bifid end gives rise to the two lobes of thyroid
gland. Dr.Barkha.S.Tiwari 29

 The thyroid gland is covered by a fibrous capsule which on
microscopic examination is seen as aggregation of follicles.
 Each follicle is lined by follicular cells
 Apart from that the gland also contain C-cells(parafollicular
cells) which intervene between the follicular cells and the
basement membrane.

 The shape of the follicular cells
vary on their level of activity.
When :
Normal – cells are cuboidal
and colloid is moderate
Inactive – cells are flat and
colloid is abundant
Highly active- cells are
columnar and colloid is
scanty

Follicular cells:
They secrete 2 hormones T3 (triiodothyronine) and T4
(tetraiodothyronine) that influence the rate of metabolism for
which iodine is an essential component.
 The activity of follicular cells is influenced by TSH (thyroid
stimulating hormone).

The C-cells (Parafollicular cells):
 Also known as clear cells or light cells.
 They secrete hormone thyro-calcitonin which has as action
opposite to that of the parathyroid hormone on calcium
metabolism.
 This hormone comes into play when serum calcium level is
high.

 Each parathyroid gland has a connective tissue capsule
 There are two main types of cells.
 Chief cells (principal cells)
 Oxyphil cells (eosinophil cells)
Chief cells produce parathyroid hormone ( parathormone).

 Thyroid hormones
target almost every
body cell
 Can enter cells & bind
to intracellular receptors
on mitochondria & in
nucleus

Effects include:
 increased ATP production
 increased cellular metabolism, energy utilization &
oxygen consumption
 increased body temperature
 growth & development of skeletal, muscular & nervous
system in fetus & children

On The Cardiovascular System:
 Increase heart rate
 Increase force of cardiac contractions
 Increase Cardiac output
On The Respiratory System
 Increase resting respiratory rate
 Increase ventilatory response to hypercapnia and hypoxia

On The Renal System
 Increase blood flow
 Increase glomerular filtration rate
On Intermediary Metabolism
 Increase glucose absorption from the GI tract
 Increase carbohydrate, lipid and protein turnover

On The Nervous System
 Enhances wakefulness and alertness
 Enhances memory and learning capacity
 Required for normal emotional tone
On The Reproductive System
 Required for normal follicular development and ovulation in
the female
 Required for the normal maintenance of pregnancy
 Required for normal spermatogenesis in the male

 Thyroid secretes more T4 than T3
 T4 is the major circulating hormone because it is 15 times
more tightly bound to plasma proteins.
 T3 is 5 times more potent than T4 and acts faster.
 About 1/3 of T4 is converted to T3 in the thyroid cells, liver
and kidney.

 Thus it may be concluded that T3 is the active
hormone, while T4 is mainly a transport form which
functions as a prohormone of T3.

 Parathormone which is produced by the chief cells tends to
increase the serum calcium level

 Aberrant thyroid tissue may be found
 Lingual thyroid
 Red rounded swelling in the middle at the junction of anterior 2/3
and posterior 1/3 of the tongue.
 May cause speech impairment and hemorrhage

Treatment
Suppressive doses of thyroxine to reduce size of swelling
Thyroglossal ectopic thyroid:
 Forms a swelling in the upper part of the neck may be
mistaken for thyroglossal cyst.

Etiology
 Grave’s disease
 Multinodular goitre
 Iodine induced, TSH induced
 Thyroiditis-subacute (De Quervains), post partum

SYMPTOMS SIGNS
General
Weight loss despite normal or
increased appetite
Heat intolerance
Fatigue
osteoporosis
Weight loss
Goitre with bruit
Gastrointestinal
Diarrhoea ,steatorrhoea
Hyperdefecation
Anorexia
vomiting
Cardiorespiratory
Palpitations
Dyspnea on exertion
Angina
Ankle swelling
Sinus tachycardia
Atrial fibrillation
Systolic hypertension/increased
pulse pressure
Cardiac failure
Clinical features

Neuromuscular
Anxiety ,irritability ,emotional
liability
Psychosis
Tremor
Muscular weakness
Tremor
Hyper-reflexia
Ill sustained clonus
Proximal myopathy
Bulbar myopathy
Dermatological
Sweating
Pruritis
Alopecia
Pretibial myxoedema
Finger clubbing
Spider naevi
Onycholysis
Ocular
Grittiness ,red eyes
Excessive lacrimation
Diploplia
Loss of acuity
Lid retraction ,lid lag
Chemosis
Exopthalmos
Periorbital oedema
Corneal ulceration
Ophthalmoplegia
Papilloedema

Reproductive
Amenorrhoea /oligomenorrhoea
Infertility ,spontaneous abortion
Loss of libido
impotence
Gynaecomastia

 Accelerated alveolar ridge atrophy
 Premature loss of deciduous teeth
 Early eruption of permanent teeth
 Tremor of lips and tongue

 Dental caries
 Periodontal disease develop rapidly
 Increased incidence of mucosal ulcerations
 Lingual thyroid
 Burning mouth syndrome

 Serum T3 and T4 are elevated.
 Measurement of TSH receptor antibodies.
 Radio isotope scanning.

Antithyroid drugs
 Carbimazole
 Propylthiouracil
 Potassium perchlorate
 Propranolol: (Beta-blocker)
 Iodides: (temporary effect)
Reduce the effect of TSH on thyroid gland

 Destroys thyroid cells by reducing number of functioning
acini.
 Indications:
 Primary toxic goitre above the age of 40 years
 Recurrence after surgery
 Refusal of surgery
 Thyrocardiac patients

Surgery:
 Operation:
 Subtotal thyroidectomy
 Aim:
 Removing thyroid tissue & leaving an equivalent of 4-5
grams

 Haemorrhage
 Respiratory obstruction
 Laryngeal oedema
 Bilateral Recurrent laryngeal nerve injury

Patients are sensitive to following drugs.
Normal dosage may prove to be an overdose, leading to respiratory
or CVS depression or both.
Sedatives (eg., barbiturates)
Narcotics (eg,. Meperidine, codeine)
Antianxiety (eg., diazepam)
CNS depressants

 Rare and life threatening increase in clinical features of
thyrotoxicosis
 Medical emergency
Signs
 Fever, agitation, confusion, tachycardia and cardiac failure in
older patients.
 Precipitated by an infection in a patient with previously
unrecognized or inadequately treated thyrotoxicosis

 Rehydration
 Broad spectrum antibiotic
 Proponolol Orally(80 Mg 6 Hourly) or Intravenously (1-5
mg 6 hourly).

 Prevalence -1:100
 Female: male ratio=6:1
Causes
 Autoimmune
 Hashimoto’s thyroiditis
 Spontaneous atrophic hypothyroidism
 Graves disease with TSH receptor blocking antibodies

 Iatrogenic
 Radio active iodine ablation
 Thyroidectomy
 Drugs ( carbimazole, methimazole, propylthiouracil )
 Transient thyroiditis
 Subacute( De quervain’s) thyroiditis
 Post partum thyroiditis

 Congenital
 Iodine deficiency - mountainous regions
 Infiltrative - Amyloidosis, Riedels thyroiditis
 Secondary hypothyroidism - TSH deficiency

SYMPTOMS SIGNS
General
Weight gain
Cold intolerance
Fatigue ,hoarseness
Weight gain
Hoarse voice
Goitre
Gastrointestinal
constipation Ileus
Ascites
Cardiorespiratory
Bradycardia
Hypertension
Pericardial and pleural effusion
Neuromuscular
Carpal tunnel syndrome
Aches and pains
Muscle stiffness
Delayed relaxation of tendon
reflexes
Clinical features:

Dermatological
Dry skin
Dry hair
Alopecia
Myxoedema
Purplish lips
Malar flush
Ocular Periorbital oedema /myxoedema
Loss of lateral eyebrows
Reproductive
Amenorrhoea
Infertility

In a controlled Hypothyroid patient:
• Use Lidocaine , Prilocaine or Bupivacaine, maximum 2
carpules
• For stress management use 2/5 mg Diazepam or 02 + N2O
• For moderate to severe pain, use Acetaminophen with
codeine
In an uncontrolled Hypothyroid patient:
• Use Mepivacaine for L.A
• Avoid Codeine, Morphine and Diazepam

 Cretinism- in infancy or early childhood
 Myxedema- in adults

 Mental retardation
 Faces of cretinism-
disproportionately large cranium
puffy face
flat broad nose
wide set eyes

 Dull expression
 Open mouth
 Stuffy hand
 Dwarfism
 Sparse and brittle hair
 Generalized oedema

 Macroglossia
 Protruding tongue
 Malocclusion
 Delayed tooth eruption
 Retention of deciduous tooth
 Thick everted lips

 Generalised non pitting oedema
 Coarse facial features
 Thick lips
 Puffy eyelids
 Sad expression

 Lethargy
 Dry and brittle hair
 Weight gain
 Constipation

 Macroglossia
 Dysguesia
 Salivary gland enlargement (parotid and submandibular)
 Glossitis

 Compromised periodontal health
 Delayed wound healing
 Sjogren’s syndrome
Management :
Life long thyroxine therapy

 State of decompensated hypothyroidism.
 Reduced level of consciousness.
 Mortality rate is 50% and usually in elderly.
 Sometimes associated with seizures, as well as the other
features of hypothyroidism.
 Hypothermia can reach 23 degree C (74F).

 There may be a history of treated hypothyroidism with poor
compliance ,or the patient may be previously undiagnosed
 Precipitated by factors that impair respiration, such as drugs
(especially sedatives, anesthetics ,antidepressants),
pneumonia, congestive heart failure, myocardial infarction,
gastrointestinal bleeding, or cerebrovascular accidents.

 Levothyroxine can initially be administered as a single
intravenous bolus of 500 g, which serves as a loading dose
 Supportive therapy should be provided to correct any
associated metabolic disturbances

 Originally derived from Latin word gutter means throat
 Enlargement of the thyroid gland

CLASSIFICATION
Simple goitre
A) Diffuse hyperplastic goitre
B) Nodular goitre
C) Colloid goitre
Toxic goitre
A) Diffuse toxic goitre(graves disease)
B) Toxic nodular goitre

Neoplastic goitre
A) Benign tumor
B) Malignant tumor
Thyroiditis
A) Autoimmune thyroiditis
B) Subacute or granulomatous or de quervains thyroiditis
C) Riedels thyroiditis

 Etiology
 Formed due to
stimulation with
increased TSH.
 TSH secretion is
increased due to low
level of circulating
thyroid hormones.

 Familial goitre
 Endemic goitre
 Dyshormonogenesis or enzyme deficency
 Goitrogens
 -cabbage, turnips, brussel, cauliflower
 -drugs eg. thyocyanate, antithyroid drugs
 Physiological
 Sporadic

 C/f:
- mostly occurs b/w the ages of 15-25 yrs
- occurs often during pregnancy
- goitre is soft and symmetrical and the thyroid
is enlarged to 2-3 times its normal size.

 Females more affected - 9:1
 Asymptomatic
 Swelling in the neck
 If goitre too big - pressure effect on trachea or oesophagus
 Distension of jugular vein due to pressure effect
 On inspection there is diffuse swelling which moves on
swallowing

 Females
 On examination nodules may
be palpable which are
usually multiple and
asymmetric

 Nodules are usually colloid, cystic, degenerative,
haemorrhagic or may form
calcification.

 Patients above 25 years of age
 Diffuse swelling of the gland which is quite soft.
Complications
 Secondary thyrotoxicosis
 Tracheal obstruction
 Carcinoma
Treatment
 Partial thyroidectomy

 Derived from lower pole of the multinodular goitre.
 In men whose necks are short and pretracheal muscles are
strong, negative intrathoracic pressure tends to draw goitre
into superior mediastinum

According to degree of descent
 Classified into –substernal goitre
plunging goitre
intrathoracic goitre
Treatment – resection of retrosternal goitre

 There is diffuse enlargement
of the gland.
 Commonest cause of
endogenous (primary)
hyperthyroidism

 The disease results from the production of IgG antibodies
directed against the TSH receptor on the thyroid follicular
cell, which stimulate thyroid hormone production and goitre
formation.
 More common in young females & characterized by
remission & exacerbations.

 Classic clinical Triad:
1) Thyrotoxicosis and Diffusely Enlarged Thyroid
2) Exophthalmos (infiltrative Ophthalmopathy) (in 40%)
3) Pretibial myxedema (infiltrative Dermatopathy) (minority)

Signs of thyroid gland in Graves
disease:
 Uniformly enlarged
 Smooth surface – no nodules
 Gland is soft or firm in
consistency
 It is warm – highly vascular
 On auscultation – a bruit is usually
heard

 Protrusion of eye ball
 Unilateral or bilateral
 Either true or false
 True is deposition of fluid &
round cell infiltrated behind the
eye

 True is complicated by conjunctivitis & corneal ulcerations
with lid edema
 False is due to spasm of Muller’s muscles & this keeps the
eye balls forward.

 Always associated with
exophthalmos
 Bilateral symmetrical deposition of
myxomatous tissue mainly in the
pretibial region , may also affect the
foot and ankle
 Skin is dry and coarse- thickening by
mucin like deposits

 Pretibial myxoedema is non-pitting & may be associated
with clubbing of fingers & toes called thyroid acropachy

 Physical exam – by feeling your neck area for nodules and
signs of tenderness.
 Hormone test – A blood test to determine thyroid hormone
levels
 Antibody test – A blood test to look for the production of
TSH receptor (TRAb) antibodies that are produced in some
forms of goitre (mostly grave’s disease) .

 Ultrasound of the thyroid – An imaging test that reveals the
gland’s size and possible presence of nodules.
 Thyroid scan – Another imaging test that provides
information on the size and function of the gland. This test
involves the use of a small amount of radioactive material
injected into a vein.
 CT scan or MRI -These imaging tests are used to evaluate
the size and extent of the goitre.

 Appears from cystic degeneration of a part of thyroglossal
duct
 Always in the midline commonest position just below hyoid
bone
 Often complicated with infection

Treatment
 Always excised
 When present with infection and abscess formation ,incision
and drainage

 Forms following infection of
a thyroglossal cyst or
following its incomplete
removal
 Opening varies from hyoid
bone upto the isthmus
 Serous secretion is
discharged

Treatment
 Excision of the whole
thyroglossal tract through the
central core of lingual muscles-
sistrunk operation

 Bacterial infection of the thyroid
 Rare due to rich blood supply
Types
 Granulomatous thyroiditis
 Autoimmune thyroiditis
 Riedels thyroiditis

 Also called subacute thyroiditis – De Quervains disease
 Females are more affected than males.
 Occurs due to viral infection, usually follows sore throat
 Patients present with fever, bodyache and painful
enlargement of thyroid gland.

 The pain may radiate to the angle of the jaw and the ears and
is made worse by swallowing, coughing and movement of
the neck.
 The gland is enlarged, tender to touch, soft to firm and a few
symptoms of hyperthyroidism occur initially
 ESR is increased

Treatment:
 Drugs such as NSAIDS
 Prednisolone 40mg daily for 3-4 weeks
 Propranolol

 Iodine Deficiency
- Dietery deficiency of iodine especially in the mountainous
regions usually leads to thyroid enlargement which is known as
endemic goitre.
T/t:
Iodine supplementation programmes.

 Hashimoto’s thyroiditis is the main component of thyroiditis.
 Autoimmune etiology is characteristic by extensive
lymphocytic infiltration resulting in destruction of thyroid
follicles with variable degree of fibrosis which accounts for
thyroid enlargement.

 Females in premenopausal group (40-50yrs) commonly
affected
 Initially symptoms of mild hyperthyroidism may be present,
later intrathyroidal fibrosis results in permanent
hypothyroidism

Small or moderately sized diffuse goitre, which is
characteristically firm or rubbery in consistency.

 Very rare cause of a goitre
 Collagen disorder
 There is intrathyroidal fibrosis and more of extra thyroidal
fibrosis.
 Involvement of trachea, oesophagus, inter jugular vein,
carotid artery etc. result in dysphagia and dyspnoea.
 It may progress to anaplastic carcinoma
T/t:
Partial thyroidectomy.

 Benign tumors/ Toxic Adenoma- secretes excess of thyroid
hormones.
 Follicular adenoma- it is a solitary nodule which is greater
than 3cm in diameter
 Females above 40yrs are mostly affected.
 The thyrotoxicosis is mild.
T/t:
Surgical hemithyroidectomy.

Differentiated Carcinoma:
Papillary carcinoma:
• most common of the malignant thyroid tumors.
• Accounts for about 90% irradiation-induced thyroid cancer.
• It is multifocal and spreads to regional lymph nodes.

Follicular carcinoma:
• Single encapsulated lesion.
• Metastases are blood-borne and often found in bone, lungs
and brain
T/t:
Total thyroidectomy
Radioactive iodine

Hyperparathyroidism:

 Primary Hyperparathyroidism
 Autonomous secretion of PTH, usually by a single
parathyroid adenoma varying in size.
 Most common disorder
 Prevalence 1:800
 Most common in women
 Age – above 50 yrs

 Secondary Hyperparathyroidism
 Excessive production of PTH in response to decreased
level of calcium.
 Caused by conditions that interfere with calcium,
phosphate or Vit D regulation such as kidney failure,
malnutrition.

 In a very small proportion of cases of secondary
hyperparathyroidism, continous stimulation of the
parathyroids results in adenoma formation and autonomous
PTH secretion. This is known as Tertiary
Hyperparathyroidism

Cause:
Primary hyperparathyroidism
C/f:
Polyuria, polydipsia, renal colic, lethargy, anorexia, nausea,
dyspepsia, peptic ulceration, constipation, depression,
drowsiness and hypertension

 Patients with the disease are described by the adage: ‘Bones,
stones and abdominal groans’

Investigation:
• Low plasma phosphate and elevated alkaline phosphatase
• If PTH is normal or elevated and urinary calcium is elevated,
then hyperparathyroidism is confirmed.
T/t:
• Rehydration with normal saline.
• Biphosphanates.
• Prednisolone 40mg daily.
• Calcitonin

Cause:
Low serum albumin with normal ionised calcium concentration.
C/F:
Tetany- increase in the excitability of the peripheral nerves.
Children are more sensitive than adults.

 In children, a characteristic traid of carpopedal spasm, stridor
and convulsions occur, adults complain of tingling in the
hands, feet and around the mouth.
 Trosseau’s sign and Chvostek sign positive.

 Altered tooth eruption pattern
 Short blunted roots
 Enamel hypoplasia
 Dentin dysplasia
 Impacted teeth
 Partial anodontia
 Circumoral paraesthesia(facial parasthesia and facial
twitching)

Congenital hypoparathyroidism showing mottled
enamel from decreased serum calcium during tooth
calcification

Diagnosis –
Low plasma calcium
Phosphate level is often raised .
T/t:
 Replacement therapy includes vitamin D and calcium
supplements.
 Alkolosis can be reversed acutely if arterial PCO2 is
increased by rebreathing expired air in a paper bag.
 Injection of 20ml of 10% solution of calcium gluconate.

 Due to hypoplastic teeth patient has increased caries risk, so
needs frequent oral examinations.
Dental management is complicated by –
 Tetany.
 Seizures.
 Psychiatric problems or learning disability.
 Facial parasthesia and facial twitching caused by tetany.

 Fundamental anatomical knowledge of thyroid gland is an
important foundation to the knowledge bank of dentists.
 Important clinical implications in diagnosis and treatment.

 B D Chaurasia’s human anatomy regional and applied
volume 3 head neck and brain 4th edition
 Davidson’s Principles and Practice of Medicine, 18th Edition
 Textbook of Embryology by Inderbir Singh 7th edition
 Textbook of Human Histology by Inderbir Singh 6th edition
 Textbook of Clinical Medicine by S.N Chugh

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