Disorders of thyroid glands - B. Pharma 2nd Semester Pathophysiology notes pdf
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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