The document discusses disorders of the thyroid gland, including hypothyroidism and hyperthyroidism. It begins by reviewing the anatomy and physiology of the thyroid gland and hypothalamic-pituitary-thyroid feedback system. Hypothyroidism can be congenital or acquired, and if during childhood causes cretinism. Acquired hypothyroidism in adults is called myxedema. Hyperthyroidism results from increased thyroid hormone secretion and can be caused by Graves' disease. Thyroid storm is a life-threatening exacerbation of hyperthyroidism.

1. Disorders of Thyroid
Gland
Hizbullah Khan
Asst. Professor MTI CNM

2. Objectives
• Review the anatomy and physiology of thyroid
gland and hypothalamic pituitary thyroid
feedback system
• Discuss the disorders associated with thyroid
gland i.e. hypothyroidism
• Cretinism and myxedema
• Discuss disorders associated with thyroid gland
i.e. Hyperthyroidism
• Grave’s disease and Goiter

3. Thyroid gland
Anatomy of Thyroid gland
• The thyroid is a 2-inch-long, butterfly-shaped gland
weighing less than 1 ounce. The thyroid gland lies in
front of the neck below the Larynx and consists of 2
lobes: one on each side of the trachea, connected by
isthmus.
The gland has rich blood supply (i.e. highly vascular).
Histology
The thyroid gland is made up of multiple spherical acini
(follicles). Each follicle consists of a single layer of
Cuboidal cells surrounding a lumen filled with colloid
(protein in nature).

4. Thyroid gland

5. Thyroid hormones
Thyroid hormones:
1. Thyroxin (Tetra iodothyronine = T4).
2. Tri iodothyronine = T3
3. Thyrocalcitonine hormone from Para follicular cells (i.e.
between thyroid follicles). It lowers plasma Ca ++ level.
Thyroid hormones T3 and T4 are synthesized by thyroid gland:
• Iodine is essential to the thyroid gland for synthesis of its
hormones. Iodide is ingested in the diet and absorbed into the
blood in the gastrointestinal tract. The thyroid gland take up
iodide from the blood and concentrate it within its cells, where
iodide ions are converted to iodine molecules, which react with
tyrosine (an amino acid) to form the thyroid hormones.
 T3 acts more rapidly and is more active (3-5 times) than T4.
 The thyroid gland secretes T4 (80 μg / day) and T3 (4 μg / day)
i.e. in a ratio 20 : 1

6. Feedback mechanism

7. Actions of thyroid hormones:
T3 and T4 have the following effects:
1- General metabolism: Thyroid hormones increase the metabolic
rate and O2 consumption of all tissues of the body except the
adult brain, lymphoid tissues, retina and anterior pituitary gland.
2- Protein metabolism: Normal levels of thyroid hormones stimulate
protein synthesis (anabolic effect) whilst excess Thyroid
hormones secretions cause protein catabolism (breakdown of
protein molecules).
3- Carbohydrate metabolism: Thyroid hormones stimulate glucose
uptake and utilization by tissues, liver glycogenolysis and
intestinal absorption of glucose.
4- Lipid metabolism: Thyroid hormones decrease the level of lipid
and cholesterol in the blood (i.e. increased cholesterol catabolism
than lipogenesis)

8. Actions of thyroid hormones (Continued)
5- Vitamin metabolism: Thyroid hormones are essential for hepatic
conversion of carotene (in green vegetable and carrot) into vitamin A.
6- Growth and maturation: Thyroid hormones are essential for physical,
mental and sexual growth.
7- Cardiovascular effects:
 Tachycardia (i.e. increased heart rate).
 The strength of myocardial muscle is increased.
 Increased cardiac output.
 Increased systolic blood pressure with a concomitant decrease in diastolic
blood pressure. So, pulse pressure is increased.
8- Respiratory system: Thyroid hormones cause an increase in rate and depth
of breathing to increase body metabolism.
9- Gastrointestinal tract: Thyroid hormones increase appetite, digestive juice
secretion, intestinal motility.
10- Hemopoietic system: Thyroid hormones stimulate erythropoiesis by
increasing the rate of metabolism in the bone marrow and enhance
absorption of vitamin B12 from terminal ileum.

9. Hypothyroidism
 Hypothyroidism is a common endocrine disorder
resulting from deficiency of thyroid hormones.
 Hypothyroidism can occur as a congenital or as an
acquired defect.
 Hypo function of the thyroid gland during
childhood is called '‘Cretinism'' and if occurs
during adulthood, it is called '' Myxedema''.

10. Incidence:-
Congenital 1 : 5000 births
Under age 20 1 : 1500
Over age 20 1 : 150
Over age 60 1 : 50
Male / female 1 : 5
Basal metabolic rate can fall as low as 40 %

11. Etiology
Thyroid Tissue
Loss or Atrophy
Dysfunction of
Pituitary Gland
Dysfunction of
Hypothalamus
Autoimmune
Post Surgery
Post radiation
Decreased Hormone
Synthesis
Decreased Thyroxin
Production
Tumour or
surgery
Decreased TSH
Production
Decreased TRH
Production
HYPOTHYROIDISM
Primary (90%) Secondary (<10%)
Tertiary
(Rare)

12. Congenital Hypothyroidism
 It may result from congenital lack of thyroid gland or
from abnormal biosynthesis of thyroid hormone or
deficient TSH secretion.
 With congenital lack of thyroid gland, the infant usually
appears normal and functions normally at birth since
hormones have been supplied in utero by the mother.
 Thyroid hormone is essential for normal growth and
development of the brain, half of which occurs during
the first six months of life.
 Congenital hypothyroidism if untreated, causes mental
retardation and impairment of growth.

13. CRETINISM
 Hypothyroidism occurring during infancy or childhood is termed
as Cretinism.
 Causes of cretinism:
a) Congenital absence of the thyroid
b) Iodine deficiency during pregnancy.
 Features:
 Severe mental retardation due to impaired development of the
brain.
 Delay in all milestones of normal growth
 Skeletal abnormalities (e.g. short stature).
 Coarse facial features that include;
o large, bulging head and prominent scalp veins
o flat bridged nose with broad, fleshy tip
o small, widely spaced and/or malformed teeth
o hypertrophic gums, large lips & protruding tongue

15. Myxedema (Acquired Hypothyroidism)
 When hypothyroidism occurs in older children or adults
it is called acquired hypothyroidism or myxedema.
 The term myxedema is caused by an accumulation of a
hydrophilic mucopolysaccharide substance (long chains
of sugar molecules found throughout the body) in
connective tissues throughout the body.
 The hypothyroid state may be mild, with only a few
signs and symptoms, or it may progress to:
1.Primary hypothyroidism: a life-threatening
condition or dysfunction of the thyroid gland or
2.Secondary hypothyroidism: a condition, caused by
impaired hypothalamic or pituitary function

16. Primary Hypothyroidism
 It may result from thyroidectomy (surgical removal) or
ablation of the gland with radiation.
 Certain goitrogenic agents, such as lithium carbonate
(used in the treatment of manic-depressive states) and
the antithyroid drugs propylthiouracil and methimazole
in continuous dosage, can block hormone synthesis and
produce hypothyroidism with goiter.
 Large amounts of iodine can also block thyroid
hormone production and cause goiter, particularly in
persons with autoimmune thyroid disease.

17. GOITER
o It is an enlargement of the thyroid gland, associated
with Hyperthyroidism or hypothyroidism.
Types of goiter
■ Endemic goiter (i.e. in more than 10% of
population)
o The diet in the area is deficient in iodine.
o The thyroid gland enlarges so the individual can
make the best use of limited iodine in the body.
o Patients may be euthyroid as a result, even though
the gland is large.

18. GOITER
■ Sporadic goiter: Female predominance; young adults
o Sporadic goiter is due to goitrogens such as cabbage
& cauliflower which inhibit the formation of T3 & T4.
Pathogenesis of goiter
o Low levels of thyroid hormones cause an increased
level of TSH, which stimulates the thyroid gland,
causing hyperplasia & hypertrophy of follicular cells
which can lead to nodule formation.

19. Hashimoto’s Thyroiditis
 Hashimoto’s Thyroiditis is probably the most
common cause of primary hypothyroidism.
Etiology & Pathophysiology
 It results from an autoimmune response against the
thyroid gland.
 Thyroid cells are destroyed by hypersensitivity reaction
mediated by cytotoxic T-cells.
 The thyroid gland is enlarged diffusely in the beginning
that becomes smaller with disease progression.
 The end result is a markedly atrophic fibrosed thyroid.

20. Clinical Features
 There is painless enlargement of thyroid gland
with gradual development of hypothyroidism.
 Usually transient thyrotoxicosis precedes the
development of hypothyroidism, caused by the
disruption of thyroid follicles with secondary
release of thyroid hormones.
 Thyroid autoantibodies can be detected in the
serum of almost all patients.
Hashimoto’s Thyroiditis

21. Secondary Hypothyroidism
 Decreased thyroid hormones production due to failure
of TSH secretion in condition such as hypopituitarism.
 This type of hypothyroidism is rare.
Myxedema
 It affects almost all of the organ systems in the body.
The most common cause is Hashimoto’s Thyroiditis
but can be caused by impaired hypothalamic/pituitary
function. The manifestations of the disorder are largely
related to two factors;
1. The hypo-metabolic state resulting from thyroid hormone
deficiency and
2. Myxedematous involvement of the body tissues.

22. Myxedema Cont…
 The hypo-metabolic state associated with myxedema
is characterized by a gradual onset of weakness and
fatigue, a tendency to gain weight despite a loss in
appetite, and cold intolerance.
 Gastrointestinal motility is decreased, giving rise to
constipation, flatulence, and abdominal distention.
 Nervous system involvement is manifested in mental
dullness, lethargy and impaired memory.

23. Myxedema Cont…
 As a result of fluid accumulation, the face takes on a
characteristic puffy look, especially around the eyes.
 Myxedematous fluid can collect in the interstitial
spaces of almost any organ system.
 Pericardial or pleural effusion may develop.
 Mucopolysaccharide deposits in the heart cause
generalized cardiac dilatation, bradycardia and other
signs of altered cardiac function.

24. Myxedematous Coma
 Myxedematous coma is a life-threatening end-stage
expression of hypothyroidism.
 It is characterized by coma, hypothermia, cardiovascular
collapse, hypoventilation & severe metabolic disorders
that include hyponatremia, hypoglycemia and lactic
acidosis.
 It occurs most often in the elderly (above age 50) and
more frequently in winter months, suggesting that cold
exposure may be a precipitating factor.
 The severely hypothyroid person is unable to metabolize
sedatives, analgesics, and anesthetic drugs, and these
agents may precipitate coma.

26. Myxedematous Coma
 Diagnosis
o Low serum T4
o Low resin T3 (to estimate the amount of TBG in the
blood, and how much T4 and T3 in the blood is free
form and available to affect the body)
o Elevated TSH
o Antithyroid antibodies test- if hashimaoto’s
thyroiditis is suspected.

27. Hyperthyroidism
 Hyperthyroidism results from increased secretion of thyroid
hormone to the peripheral tissue.
 It is commonly associated with hyperplasia of the thyroid gland,
multi-nodular goiter and adenoma of the thyroid.
 Occasionally it develops as a result of ingestion of an overdose of
thyroid hormone.
 When the condition is accompanied by exophthalmos and goiter,
it is called graves’ disease.
 Thyroid crisis or storm, is an acutely exaggerated manifestation
of the hyperthyroid state.
Incidence:
2 - 5% of all females between age of 30-50 years
Male / female 1 : 7

28. Etiology
Secondary
(Rare)
Thyroid Tissue
Disease Over Secretion
by Pituitary
Autoimmune
(Graves Disease)
Thyroid Stimulating
Antibodies
Increased Stimulation
of TSH Receptors
Increased Thyroxin
Production
Pituitary
Tumor
HYPERTHYROIDISM
Increased TSH
Production
Primary (99%)

29. Hyperthyroidism
 Many of the manifestations of hyperthyroidism are
related to the increase in oxygen consumption,
associated with hyper-metabolic state as well as the
increase in sympathetic nervous system activity.
 Many of the signs/symptoms of hyperthyroidism
resemble those of excessive sympathetic activity. It
suggest that:
o Thyroid hormones may heighten the sensitivity
of the body to the catecholamines (Epinephrine
and norepinephrine or
o Thyroid hormones itself may act as a pseudo
catecholamine.

30. Hyperthyroidism
 With the hyper-metabolic state, there are frequent
complaints of nervousness, irritability and fatigability.
Weight loss is common despite a good appetite.
 Other manifestations include tachycardia, palpitations,
SOB, excessive sweating, heat intolerance and muscle
tremor.
 The hair and skin are usually thin and have a silky
appearance.
 Hyperthyroidism can be treated by anti-thyroid drugs
(e.g. carbimazole), radioactive iodine or surgery.

31. Graves’ Disease
 Graves’ disease is a state of hyperthyroidism, goiter,
and exophthalmos. It is the most common cause of
endogenous hyperthyroidism.
Etiology
 It is an auto-immune disease, characterized by the
presence of auto-antibodies in the serum, directed
against TSH receptors in the thyroid cells.
 The antibodies continuously stimulate the TSH
receptors and thyroid cells produce T3 and T4 in
excess.

32. Graves’ Disease
Autoimmune disease
Excessive production of TWO thyroid auto antibodies:
1) Thyroid-stimulating antibody (TSAb)
2) Growth-stimulating antibody (GSAb)
Antibodies bind to the TSH receptor of the follicular cell
Stimulation of the cell resulting in:
Increased levels of thyroid hormones &
Hyperplasia of the thyroid gland
Hyperthyroidism and Thyroid gland enlargement

33. Clinical Features
 Diffuse enlargement of thyroid gland that appears as a
mass in the neck.
 Opthalmopathy characterized by staring gaze, wide
open eyes, reduced eye movements and decreased
blinking
 Protruded eye balls, called exophthalmos, due to
mucopolysaccharide-rich tissues deposition behind
the eyeball.
Investigations
1) Elevated T3, T4 and depressed TSH
2) Radioiodine scan shows diffuse uptake of iodine.
Graves’ Disease

34. Thyroid storm
 Thyroid storm is an extreme and life threatening form of
thyrotoxicosis, most of the times in patients with
underlying Grave’s Disease.
 It is often precipitated by stress, such as infection,
diabetic ketoacidosis & physical or emotional trauma.
 Thyroid storm is manifested by a very high fever,
extreme cardiovascular effects and severe CNS effects.
Mortality rate is high due to cardiac arrhythmias.
 Thyroid storm requires rapid diagnosis (free T4 elevated)
and implementation of treatment (anti-thyroid drugs,
radioiodine and subtotal thyroidectomy).

35. Hyperthyroidism (Manifestation of Thyrotoxicosis:)
1. General metabolism:
a) B.M.R is increased up to +100 %.
b) Patient can not tolerate heat.
2. Protein metabolism:
Excess T3 and T4 cause protein catabolism manifested by:
 Loss of body weight
 Muscle weakness and easy fatigability.
 Osteoporosis (i.e. decreased bone matrix density)
 Hypercalcemia in 20% of patients
3. Carbohydrate metabolism:
Glucose absorption, glycogenolysis and gluconeogenesis
are stimulated.

36. Hyperthyroidism
Manifestations- continued
4. Lipid metabolism:
Blood cholesterol and lipids are decreased.
5. Vitamins, Minerals and water metabolism:
 Ca++, PO4‾ ‾ ‾ and water exertion in the urine are increased.
6. Nervous system:
 The patient is irritable, restless, anxious, and emotionally unstable and is
unable to sleep (i.e. insomnia).
 Fine tremors in the tongue and outstretched fingers.
 Deep tendon reflexes are exaggerated.
7. Cardiovascular system.
o Heart rate is increased (i.e. tachycardia )
o Sleeping pulse usually above 100 beats / minute.
o Cardiac output and systolic blood pressure are increased.
o Pulse pressure is increased (i.e. the difference between systolic and diastolic
blood pressure)

37. Hyperthyroidism
Manifestation - Continued
8. Respiratory system.
• Vital capacity is reduced due to respiratory muscle asthenia.
• High thyroid hormone levels induce hyperventilation and an
increase of ventilatory response to hypoxia and hypercapnia
9. Gastrointestinal tract:
• Increased appetite but body weight is decreased due to increased
metabolism.
• Liver cell failure (due to glycogen depletion from liver cells).
• increased frequency of bowel movements : Diarrhea (loose
watery stool).
10. Skin:
• Warm and flushed due to vasodilatation.
• Moist due to excessive sweating.

38. References
1. Danish MI. Short text book of pathology. 4th edition;
2010. Johar Publications, Karachi-Pakistan.
2. Emanuel Rubin, and John L. Farber, Essential
Pathology, Philadelphia, 1990
3. Cotran RS, Kumar V, Collins T. Robins pathologic basis
of diseases. Philadilphia, J.B. Saunders Company. 6th
edition 1999