Disorders of thyroid glands
Content
•
Thyroid
gland
• Disorders of thyroid glands
• Hyperthyroidism
• Hypothyroidism
• Goiter
• Thyroiditis
• Etiology and clinical features
• Thyroid cancer
Objective
At the end of the PDF Notes, the students will
be able to
• Define Thyroid gland and disorders of thyroid glands
• Discuss the etiology and clinical features
Hyperthyroidism and Hypothyroidism
• Etiopathogenesis and clinical
features of goiter and thyroiditis
• Briefly explain thyroid cancer
Thyroid Disease
Thyroid Gland
• The thyroid gland in an adult weighs
15-40 gm and is composed of two lateral lobes connected in the midline by a
broad isthmus which may have a pyramidal lobe extending upwards
HYPERTHYROIDISM (THYROTOXICOSIS)
• Hyperthyroidism, also called
thyrotoxicosis, is a hypermetabolic clinical and biochemical state caused by
excess production of thyroid hormones
ETIOPATHOGENESIS
• 3 most common causes are:
1) Graves’ disease (diffuse toxic
goitre),
2) toxic multinodular goitre
3) toxic adenoma
Other causes
Ø hypersecretion of pituitary TSH by a
pituitary tumour
Ø hypersecretion of TRH
Ø Thyroiditis
Ø metastatic tumours of the thyroid
Ø struma ovarii
Ø congenital hyperthyroidism in the
newborn of mother with Graves’ disease
Ø hCG-secreting tumours due to mild thyrotropic
effects of hCG (e.g. hydatidiform mole, choriocarcinoma and testicular
tumours),
Ø Excessive doses of thyroid hormones
or iodine called jodbasedow disease
CLINICAL
FEATURES
•
• heat intolerance
• sweating
• weight loss despite good appetite
• shakiness
• inappropriate anxiety
• palpitations of the heart
• shortness of breath,
• tetchiness and agitation,
• poor sleep
• thirst
• nausea
• increased frequency of defecation
Hypothyroidism
• It is a hypometabolic clinical state
resulting from inadequate production of thyroid hormones for prolonged periods,
or rarely, from resistance of the peripheral tissues to the effects of thyroid
hormones
1.
Cretinism or congenital
hypothyroidism -infancy and childhood.
2. Myxoedema
- adulthood
Cretinism
• Hypothyroidism present at birth or
developing within first two years of postnatal life.
ETIOPATHOGENESIS.
The causes of
congenital hypothyroidism are as follows:
Myxoedema
• The adult-onset severe
hypothyroidism causes myxoedema
ETIOPATHOGENESIS
1. Ablation
of the thyroid by surgery or radiation.
2.
Autoimmune (lymphocytic) thyroiditis (termed primary idiopathic myxoedema).
3. Endemic
or sporadic goitre.
4.
Hypothalamic-pituitary lesions.
5. Thyroid
cancer.
6.
Prolonged administration of anti-thyroid drugs.
7. Mild
developmental anomalies and dyshormonogenesis
• cold intolerance
• mental and physical lethargy
• constipation
• slowing of speech and intellectual
function
• puffiness of face
• loss of hair and altered texture of
the skin
THYROIDITIS
• Inflammation of the thyroid- Due to non-infectious causes
Classification of Thyroiditis
I. Acute
thyroiditis:
1.
Bacterial infection e.g. Staphylococcus, Streptococcus.
2. Fungal
infection e.g. Aspergillus, Histoplasma, Pneumocystis.
3. Radiation
injury
II.
Subacute thyroiditis:
1. Subacute
granulomatous thyroiditis (de Quervain’s thyroiditis, giant cell thyroiditis, viral
thyroiditis)
2. Subacute
lymphocytic (postpartum, silent) thyroiditis
3.
Tuberculous thyroiditis
III.
Chronic thyroiditis:
1.
Autoimmune thyroiditis (Hashimoto’s thyroiditis or chronic lymphocytic
thyroiditis)
2. Riedel’s
thyroiditis (or invasive fibrous thyroiditis)
HASHIMOTO’S (AUTOIMMUNE, CHRONIC LYMPHOCYTIC) THYROIDITIS
• Hashimoto’s thyroiditis, also called
diffuse lymphocytic thyroiditis, struma lymphomatosa or goitrous autoimmune
thyroiditis
ETIOPATHOGENESIS
- autoimmune disease association
- Immune destruction of thyroid
cells
- Detection of autoantibodies
- Inhibitory TSH-receptor
antibodies
- Genetic basis
GRAVES’ DISEASE (DIFFUSE TOXIC GOITRE)
• Graves’ disease, also known as
Basedow’s disease, primary hyperplasia, exophthalmic goitre, and diffuse toxic
goitre
• Characterised by a triad of
features:
1.
Hyperthyroidism (thyrotoxicosis)
2. Diffuse
thyroid enlargement
3.
Ophthalmopathy
ETIOPATHOGENESIS OF GRAVES’ DISEASE
• 1. Genetic factor association: HLA-DR3 (Hashimoto’s thyroiditis has
both HLA-DR3 and HLA-DR5 association) CTLA-4 and PTPN22 (a T-cell
regulatory gene).
• 2. Autoimmune disease association:
Other factors. Besides
these two factors, Graves’ disease has higher prevalence in women (7 to 10
times), and association with emotional stress and smoking
• 3. Other factors
• 4. Autoantibodies: TSI, TGI, TBII
GOITRE
• Thyroid enlargement caused by compensatory hyperplasia and hypertrophy of the follicular epithelium -thyroid hormone deficiency
Pathogenesis of Goitre
• Nodular goitre is generally regarded
as the end-stage of long-standing simple goitre
ETIOLOGY OF GOITRE
• Goitre occurs in 2 forms: endemic,
and non-endemic or sporadic
Endemic
goitre:
Mountainous
regions-iodine content of drinking water and food
_ Genetic
factors, Goitrogens
Sporadic
(non-endemic) goitre:
_ Suboptimal
iodine intake in conditions of increased demand as in puberty and pregnancy.
_ Genetic
factors.
_ Dietary
goitrogenes.
_
Hereditary defect in thyroid hormone synthesis and transport
_ Inborn
errors of iodine metabolism
Nodular Goitre (Multinodular Goitre, Adenomatous Goitre)
• It is the end-stage of long-standing
simple goitre. It is characterised by most extreme degree of tumour-like
enlargement of the thyroid gland and characteristic nodularity
THYROID TUMOURS
• Tumours of the thyroid are of
follicular epithelial origin; a few arise
from parafollicular C-cells
• thyroid carcinoma is the most common
type
FOLLICULAR ADENOMA
• In
adult women
• an adenoma is small (up to 3 cm in
diameter) and spherical.
THYROID CANCER
Summary
• Hyperthyroidism, also called
thyrotoxicosis, is a hypermetabolic clinical and biochemical state caused by
excess production of thyroid hormones
• Hypothyroidism is a hypometabolic
clinical state resulting from inadequate production of thyroid hormones for
prolonged period
• Thyroiditis -Inflammation of the
thyroid- Due to
non-infectious causes
• Goitre-Thyroid enlargement caused by
compensatory hyperplasia and hypertrophy of the follicular epithelium -thyroid
hormone deficiency
• Tumours of the thyroid are of follicular epithelial origin; a few arise from parafollicular C-cells
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