Disorders of Thyroid Glands

Disorders of thyroid glands

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

•      Fatigue

•        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

CLINICAL FEATURES

•       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

1. autoimmune disease association
2. Immune destruction of thyroid cells
3. Detection of autoantibodies
4. Inhibitory TSH-receptor antibodies
5. 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

Disorders of thyroid glands PDF Notes

FAQ related to Disorders of thyroid glands:

Thyroid Gland:

Q1: What is the thyroid gland, and where is it located in the body?

A: The thyroid gland is a butterfly-shaped gland located in the neck, just below the Adam’s apple.

Q2: What is the primary function of the thyroid gland?

A: The primary function of the thyroid gland is to produce hormones, mainly thyroxine (T4) and triiodothyronine (T3), which regulate the body’s metabolism.

Q3: How does the thyroid gland regulate metabolism?

A: Thyroid hormones control the rate at which the body’s cells convert oxygen and calories into energy, thus regulating metabolism.

Q4: Can problems with the thyroid gland affect other body functions?

A: Yes, thyroid gland disorders can affect a wide range of body functions, including energy levels, temperature regulation, heart rate, and more.

Disorders of Thyroid Glands:

Q5: What are some common disorders of the thyroid gland?

A: Common disorders include hyperthyroidism, hypothyroidism, goiter, thyroiditis, and thyroid cancer.

Q6: Are thyroid disorders more common in women than in men?

A: Yes, thyroid disorders, especially autoimmune conditions, are more common in women.

Q7: Can genetics play a role in thyroid disorders?

A: Yes, there can be a genetic predisposition to thyroid disorders, especially if they run in the family.

Hyperthyroidism:

Q8: What is hyperthyroidism, and what causes it?

A: Hyperthyroidism is a condition where the thyroid gland produces an excessive amount of thyroid hormones. It can be caused by conditions like Graves’ disease or thyroid nodules.

Q9: What are the common symptoms of hyperthyroidism?

A: Symptoms include weight loss, rapid heartbeat, anxiety, trembling hands, and heat intolerance.

Q10: How is hyperthyroidism diagnosed and treated?

A: Diagnosis involves blood tests and imaging. Treatment options include medication, radioactive iodine therapy, and in some cases, surgery to remove part of the thyroid gland.

Hypothyroidism:

Q11: What is hypothyroidism, and what are its causes?

A: Hypothyroidism is when the thyroid gland produces too few thyroid hormones. Causes include autoimmune thyroiditis, certain medications, and iodine deficiency.

Q12: What are the symptoms of hypothyroidism?

A: Symptoms include fatigue, weight gain, cold intolerance, depression, and dry skin.

Q13: How is hypothyroidism managed and treated?

A: Hypothyroidism is typically managed with synthetic thyroid hormone replacement therapy, such as levothyroxine.

Goiter:

Q14: What is a goiter, and what causes it?

A: A goiter is an enlarged thyroid gland. It can be caused by iodine deficiency, inflammation, or thyroid dysfunction.

Q15: Are goiters usually associated with overactive or underactive thyroid glands?

A: Goiters can be associated with both hyperthyroidism and hypothyroidism, depending on the underlying cause.

Q16: What are the treatment options for goiter?

A: Treatment depends on the cause and may include medication, iodine supplements, or surgery to remove the goiter.

Thyroiditis:

Q17: What is thyroiditis, and how is it different from other thyroid conditions?

A: Thyroiditis is inflammation of the thyroid gland. It can be caused by viral infections, autoimmune conditions, or medication side effects.

Q18: What are the common causes and symptoms of thyroiditis?

A: Common causes include viral infections and autoimmune diseases. Symptoms may include neck pain, fever, and changes in thyroid hormone levels.

Q19: Can thyroiditis be acute or chronic, and how is it managed?

A: Thyroiditis can be acute or chronic. Acute cases are often managed with pain relief and anti-inflammatory medications. Chronic cases may require long-term thyroid hormone therapy.

Thyroid Cancer:

Q20: What is thyroid cancer, and what are the risk factors for developing it?

A: Thyroid cancer is the uncontrolled growth of thyroid cells. Risk factors include radiation exposure and family history.

Q21: What are the common signs and symptoms of thyroid cancer?

A: Common symptoms include a lump in the neck, difficulty swallowing, and changes in voice.

Q22: How is thyroid cancer diagnosed and treated?

A: Diagnosis involves imaging and biopsy. Treatment may include surgery, radioactive iodine therapy, and in some cases, radiation or chemotherapy.

Disorders of thyroid glands PDF Notes