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Applied Pathophysiology > Thyroid Disorders > Flashcards

Thyroid Disorders Flashcards

1
Q

What does the Thyroid gland control?

A
  • Growth & development
  • Metabolism
  • Cardiovascular
  • Iodine metabolism
  • Calcium homeostasis
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2
Q

What does the Parathyroid gland control?

A
  • Calcium homeostasis
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3
Q

What is the anatomy of thyroid gland?

A

Located in the anterior neck, just below the larynx and close to the first part of the trachea

Two lobes on either side of the trachea (butterfly shape)

Each lobe is divided into many small lobules that contain thyroid follicles

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4
Q

What are the cell types of the thyroid gland?

A
  • Follicular cells
  • Parafollicular cells (C cells)
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5
Q

What hormone do Follicular cells produce?

A

Thyroid hormone (thyroxine and triiodothyronine)*

*: T4 is converted to T3 in the liver, kidney, and other tissues.

Biological activity: T4 < T3

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6
Q

What is the function of Follicular cells?

A
  • Growth and development
  • Metabolism
  • Cardiovascular
  • Iodine metabolism
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7
Q

What hormone do Parafollicular cells (C cells) produce?

A

Calcitonin

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8
Q

What is the function of Parafollicular cells (C cells)?

A

Calcium homeostasis

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9
Q

What doe thyroid hormones affect?

A

Thyroid hormones affect every cells and all organs of the body.

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10
Q

What are the functions of thyroid hormones?

A
  1. Growth and development
    - Bone: Promote normal growth and skeletal development in conjunction with growth hormone (GH)
    - Central nervous system: Promote normal brain development (important in utero and in early childhood)
  2. Metabolism
    - Increase basal metabolic rate (BMR)
    - Increase oxygen consumption and heat production (ñbody temperature)
    - Increase sweating (due to increased body temperature, also due to increased activity of sympathetic nervous system)
  3. Cardiovascular
    - Increase heart rate and cardiac output
  4. Iodine metabolism
    - Iodine – An important component of thyroid hormones
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11
Q

What is the regulation of thyroid hormone secretion?

A

Hypothalamus –TRH–> Anterior pituitary (Thyrotroph) –TSH–> Thyroid gland –> Thyroid hormone (Thyroxine (T4)
Triiodothyronine (T3))

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12
Q

What is the function of TSH (Thyroid stimulating hormone)?

A
  • To promote thyroid follicle development
  • To stimulate the synthesis and secretion of thyroid hormones
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13
Q

What happens when the Thyroid gland overproduces T4 & T3?

A

NEGATIVE FEEDBACK

INHIBITION of TRH, TSH, T4 & T3

= return to normal levels

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14
Q

What happens when the Thyroid gland underproduces T4 & T3?

A

NEGATIVE FEEDBACK

STIMULATION of TRH, TSH, T4 & T3

= return to normal levels

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15
Q

What are the primary vs. secondary failure?

A

Primary failure:
- damages Final endocrine gland (ex: Thyroid gland)

Secondary failure:
- damages Pituitary

Both lead to: Abnormal (increased or reduced) hormone secretion

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16
Q

What are the HYPERthyroidism clinical manifestations?

A

Increased overall metabolism
- Increased basal metabolic rate (BMR)
- Weight loss with increased appetite
- Higher body temperature
- Heat intolerance (impaired ability to adapt to heat stress)
- Hot skin
- Increased sweating

Tachycardia (increased heart rate)
Palpitations

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17
Q

Primary hyperthyroidism:

A

Defects in thyroid gland itself

Over-secretion of thyroid hormones by the thyroid

18
Q

Secondary hyperthyroidism (rare):

A

Defects in pituitary

Increased secretion of TSH

19
Q

What are the Hyperthyroidism causes?

A
  1. Graves’ disease (most common cause of hyperthyroidism)
  2. Toxic nodule
  3. TSH-secreting pituitary adenoma (Secondary hyperthyroidism)
20
Q

Graves’ disease:

A

Autoimmune disease - increased production of TSH receptor antibody, thyroid stimulating immunoglobulin [TSI]
TSI binds to TSH receptor and mimics the action of TSH (stimulates thyroid hormone secretion)

Most common cause of hyperthyroidism

Graves’ disease-specific clinical manifestations
Exophthalmos: Inflammation of extraocular muscles and periorbital tissue leading to bulging of the eyes

21
Q

Toxic nodule:

A

Non-cancerous growth(s) develop in the thyroid and produce excessive amounts of thyroid hormone

Independent of the pituitary and secretes excess thyroid hormone

22
Q

TSH-secreting pituitary adenoma (Secondary hyperthyroidism):

A

Increased TSH secretion –> Increased thyroid hormone secretion

23
Q

How do you diagnose Hyperthyroidism?

A

Blood test (TSH) – Primary vs. secondary

Blood test (T4 and T3)

24
Q

How do you diagnose Graves’ disease (Exophthalmos) (hyperthyroidism)?

A

Blood test (TSI)
Radioactive iodine uptake test (elevated uptake of radioactive iodine spread evenly in the thyroid gland)

25
Q

How do you diagnose Secondary hyperthyroidism –THS-secreting pituitary adenoma?

A

Imaging analysis (MRI, CT) –confirmation of adenoma

26
Q

What is the treatment for hyperthyroidism?

A
  1. Medication
    - Anti-thyroid medications
    – Methimazole: Inhibition of thyroid hormone synthesis
    – Propylthiouricil: Inhibition of thyroid hormone synthesis and
    peripheral conversion of T4 to T3 – Beta–blockers: Hyperthyroidism speeds up many physiological
    functions
  2. Radioiodine ablation therapy (radioiodine therapy)
  3. Surgical removal of thyroid gland (thyroidectomy)
27
Q

What are the possible problems with HYPERthyroidism?

A

HYPOthyroidism
- Over-response to anti-thyroid medication
- Overkill of thyroid gland by radioiodine therapy
- Excessive removal of thyroid gland by surgery

28
Q

What are the HYPOthyroidism clinicial manifestations?

A

Low overall metabolism
- Low basal metabolic rate (BMR)
- Weight gain
- Low body temperature
- Cold intolerance (impaired ability to adapt to cold stress)
- Decreased sweating
- Dry skin

  • Sleepiness and tiredness
  • Lower heart rate
29
Q

Primary hypothyroidism:

A

Defects in thyroid gland itself

30
Q

Secondary hypothyroidism (rare):

A

Defects in the pituitary

Lack of or reduction of both thyroid hormone and TSH

31
Q

What are the causes of primary hypothyroidism?

A

Defects in thyroid gland itself

  1. Hashimoto’s thyroiditis (most common) – Autoimmune disease
    - Production of abnormal antibodies against thyroid peroxidase (TPOAb), an enzyme important for the production of thyroid hormones
  2. Iodine deficiency
    - Lack of adequate iodine in the diet
  3. Surgical removal of thyroid gland
  4. Over-response to anti-thyroid medication
    - Anti-thyroid drugs that inhibit thyroid hormone synthesis and conversion of T4 to T3.
32
Q

What are the causes of Secondary hypothyroidism?

A

Defects in the pituitary - Pituitary adenoma, pituitary damage

33
Q

What is the diagnosis of hypothyroidism?

A

TSH level – primary vs. secondary
T4 and T3 levels
Level of antibodies – Hashimoto’s thyroiditis (TPOAb)

About 90% of cases

People with thyroid function tests showing an abnormal TSH but normal T4 and T3 levels may have subclinical (or mild) hypothyroidism or hyperthyroidism. These people may have no signs or symptoms.

34
Q

What is the treatment for hypothyroidism?

A

Thyroid hormone replacement therapy

Synthetic thyroxine (T4) – more stable form of thyroid hormone

Iodine supplementation (if the cause is insufficient dietary iodine)

35
Q

What is Goiter?

A

Prolonged stimulation of thyroid gland by TSH (or TSH-like agent) –> Excessive growth of thyroid
–> Diffuse thyroid enlargement (Goiter)

36
Q

What are the causes of Goiter?

A
  • Iodine deficiency (by TSH)
  • Hashimoto’s thyroiditis (by TSH)
  • Secondary hyperthyroidism (by TSH)
  • Graves’ disease (by TSI)
37
Q

Goiter:

A

Prolonged stimulation of thyroid gland by TSH (or TSH-like agent)

38
Q

What are the 2 causes of Goiter and what do they result in?

A
  1. Most common cause of goiter
    Iodine deficiency hypothyroidism
    A lack of iodine (insufficient iodine in the diet)
  2. Hashimoto’s thyroiditis TPOAb

both:

decrease
TSH secretion
Excessive growth of thyroid (Goiter)

Negative feedback

increase TSH secretion

lead to Excessive growth of thyroid (Goiter)

39
Q

What is the difference between Secondary hyperthyroidism and Grave’s disease?

A

Secondary hyperthyroidism
increase TSH secretion

Graves’ disease increase TSI

= Excessive growth of thyroid (Goiter)

40
Q

Thyroid disorders in children (pediatric):

A

Most thyroid diseases seen in adults also occur in children.

Congenital hypothyroidism (1 in 2,000-4,000 newborn babies) Possible cause: Failure of the thyroid gland to grow before birth
Neonatal screening by a thyroid blood test: High TSH and low T4
Growth retardation and mental disabilities
No change in intelligence if hypothyroidism develops after two years of age Thyroid hormone treatment (normal growth and prevents mental disabilities)

Hashimoto’s thyroiditis
- Most common cause of hypothyroidism in both children and adults Thyroid hormone replacement therapy

Graves’ disease
- Extreme restlessness and short attention span
- Anti-thyroid medication, thyroidectomy, and radioiodine therapy

Diagnostic test (assessment of thyroid function)
- Blood levels of thyroid hormone (T4) and TSH

41
Q

Thyroid disorders in elderly (geriatric):

A

Increased prevalence of thyroid disease with age
Slightly lower thyroid function and slightly increased TSH in older people Hypothyroidism: Most common thyroid condition in individuals over 60 years of age

Hypertyroidism
Causes
Graves’ disease - a common cause of hyperthyroidism (same as younger people)
***Toxic nodule - more frequent in older individuals than in younger individuals

Difficulties in diagnosis
- Individuals over 65 years show that thyroid illness is often undiagnosed. Symptoms are not always as widespread or obvious as those in younger patients.

Applied Pathophysiology (34 decks)

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