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Endocrine > Rat 1 > Flashcards

Rat 1 Flashcards

1
Q

Thyroid gland

A
  • Butterfly shaped

- Secretes thyroid hormones

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2
Q

Thyroid hormones

A

Influence functions of virtually all organ systems. *Children- normal growth + development. Adults- Maintain metabolic stability and homeostasis. (metabolic effects, cardiovascular effects and thermogenic effects)

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3
Q

What does the thyroid gland do with iodine?

A

Iodine can be found in regular diet (iodize salt). Uses iodine to make thyroid hormones

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4
Q

What makes T4 different from T3?

A

Unlike T4, T3 is 4x biologically potent, receptor affinity is 10-15x more, and is mainly produced from broken down T4 once in the peripheral tissue (20% produced in thyroid)

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5
Q

What are target tissues for T3?

A

Heart, nerves, bone, liver, muscle and glands

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6
Q

Describe the Hypothalamic- Pituitary- Thyroid (HPT) Axis

A

The hypothalamus releases (TRH: thyrotropin-releasing hormone) triggering the pituitary to release (TSH: thyroid- stimulating hormone). The thyroid gland is triggered by TSH to produce T4 and T3. T4 goes into the peripheral tissues to be converted to T3 as well.

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7
Q

What happens in hyperthyroidism? (Primary)

A

The thyroid produces large amounts of T3 and T4, which, through negative feedback inhibition, suppress TSH secretion from the anterior pituitary

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8
Q

What happens in hypothyroidism?

A

The thyroid produces insufficient amounts of T3 and T4, which leads to loss of negative feedback inhibition, and increased production of TSH from the anterior pituitary

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9
Q

What is usually screened for patients suspected of thyroid problems?

A

TSH

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10
Q

What happens in hyperthyroidism? (Secondary)

A

The anterior pituitary produces large amounts of TSH, which, in turn, stimulate the thyroid follicular cells to secrete thyroid hormones in excessive amounts

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11
Q

Define thyrotoxicosis

A

Excessive level of thyroid hormone by any cause. (Hyperthyroidism is a potential cause)

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12
Q

Define hyperthyroidism

A

Overproduction of thyroid hormone by thyroid gland

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13
Q

Define thyroid storm

A

Sudden release of thyroid hormone by thyroid gland

Life threatening emergency

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14
Q

Who gets affected by hyperthyroidism?

A

More women get it than men and it affects 0.5% of population

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15
Q

Etiology of hyperthyroidism

A
  • Graves’ disease: Most common cause, auto immune disease
  • Thyroid adenoma
  • Excess TSH production
  • Drug induced: amiodarone, iodinated contrast, lithium
  • Interacts with Biotin (lab assay)
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16
Q

How can patients present hyperthyroidism?

A
  • Heating intolerance
  • Increased HR: palpitations
  • Increased BP
  • Bulging eyes (exophthalmos)
  • Goiter
  • Unintentional weight loss
  • Amenorrhea
  • Anxiety/ nervousness
  • Diarrhea
  • Fatigue
  • Menstrual disturbances
  • Fine hair
17
Q

Define the normal ranges for TSH, T4, and T3

A

TSH: 0.5 - 4.7 mIU/L
T4: total: 4.5 - 10.9 mcg/dL free: 0.8 - 2.7
T3: total: 60 - 181 ng/dL
free: 2.3 - 4.2 pg/mL

18
Q

Laboratory findings for hyperthyroidism

A

Decreased TSH and increased T4, T3

19
Q

Laboratory findings for hypothyroidism

A

Increased TSH and decreased T4, T3

20
Q

What are goals of therapy for hyperthyroidism?

A
  • Eliminate excess thyroid hormone
  • Provide symptomatic relief
  • Minimize long-term consequences of hyperthyroidism
21
Q

How do you approach treatment for hyperthyroidism?

A

Treatment is individualized and is based on disease severity, gender, age and response to previous therapy

22
Q

Antithyroid Drugs (ATD): Thionamides

A
  1. Drug of Choice: Methimazole (MMI)
  2. Place in therapy: 1st line option for hyperthyroidism
  3. Goal of therapy: Achieve normal thyroid hormone levels
  4. MOA: Prevents synthesis and release of thyroid hormones
23
Q

Name another thionamide

A

Propylthiouracil (PTU) which is dosed 300-600 mg/day divided 3-4 doses. Maintenance: 100-150 mg/day divided into 3 doses

24
Q

How is methimazole dosed?

A

Dosed based on free T4 levels (generally 10-30mg/day) Free T4 1-1.5x ULN: 5-10mg once daily—
Free T4 >1.5 – 2x ULN: 10-20mg once daily—
Free T4 >2x ULN: 20-40mg/day
Maintenance: 5-10 mg/day PO QD

25
Q

Monitoring parameters for thionamides

A
  • TSH, free T4, and T3 every 4 – 8 weeks until euthyroid
  • Monitor every 2 – 3 months until euthyroid
  • Euthyroid for 1 year after discontinuation = remission
  • Follow-up after remission – about every 6-12 months
26
Q

When do you titrate thionamides?

A

Every 4 weeks

27
Q

Thionamide ADR

A 
Mild:
- Pruritic maculopapular rash
- Fever
- Arthralgias
- Leukopenia (<4,000/mm3)
- GI discomfort and nausea
- Lupus like syndrome
Serious:
- Hepatotoxicity (higher risk with PTU)
- Agranulocytosis
28
Q

Counseling points for thionamide

A
  1. Contact primary care provider if mild symptoms occur
  2. Contact doctor if you are/become pregnant
  3. Symptoms should improve in weeks to months
29
Q

What is antiadrenergic therapy for?

A

To be used as symptomatic management. The BB Propranolol is preferred with an initial dose of 10-40 mg 3/4 times daily. The target HR is < 90 BPM

30
Q

Place of iodides

A

Used to acutely inhibit thyroid hormone release:

  • 7-10 days pre-op for Graves’ disease surgery
  • Follow up for radioactive iodine, 3-7 days post-op
31
Q

When can symptom improvements and decreased T4, T3 be seen?

A
  1. Symptoms improvements occur 2-7 days

2. It takes several weeks to see decreased thyroid hormones

32
Q

Iodide ADR

A
  • Exacerbation of hyperthyroidism
  • Hypersensitivity
  • Salivary gland swelling
  • “iodism”
  • Gynecomastia
33
Q

Radioactive Iodine summary

A
  1. Place in therapy: Graves’ disease, toxic autonomous nodules and toxic multinodular goiter
  2. Goal of therapy: Destroy (ablate) overactive thyroid cells
  3. Dose: One time dose of 5-15 mCi. Colorless, tasteless liquid
  4. Euthyroid: Occurs in 6- 12 months. Can get a second dose after 6 months if not euthyroid
34
Q

Radioactive Iodine warnings and precautions

A
  1. Acute adverse reaction: dysphagia, thyroid tenderness
  2. Long term risks: increased bowel/thyroid cancer. Increases risk of mortality
  3. Contraindications: Pregnancy, lactation, and inability to adhere to radiation safety
  4. Cardiac disease or elderly: Give thionamide 4 days before and after RAI; consider BB

Endocrine (1 decks)

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