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Pharmacology > Endocrine > Flashcards

Endocrine Flashcards

1
Q

What controls the Thyroid Gland in the body and its secretions?

A

1- Hypothalamus:
Secretes TRH (Thyroid Releasing Hormone)
Onto Anterior Pituitary Gland

2- Anterior Pituitary Gland:
Secretes TSH (Thyroid Stimulating Hormone)
Onto Thyroid Gland

3- Thyroid Gland:
Secretes TH (Thyroid Hormones)
T3 - Triiodothyronine (more active form)
T4 - Thyroxine (less active form)

Need Thyroglobulin + Iodine, and the enzyme Thyroid Peroxidase, to make TH

TEST:
Order TFT (Thyroid Function Test) to check on TH, TRH, and TSH levels

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2
Q

What does TH affect in the body?

A

1- Metabolic:
Energy levels
Body temperature
Weight
Lipids - Hypercholesterolemia if hypothyroidism (low TH)
Appetite

2- Cardiovascular:
HR
Heart rhythm - severe hyperthyroidism can lead to Atrial Fibrillation and other arrhythmias
BP
Fluid distribution - Lower leg edema (pretibial)

3- Skin & Hair:
Composition
Thickness - thinning and loss
Texture

4- GI:
Motility - Diarrhea if hyper, constipation if hypo

5- Musculoskeletal:
Bone growth
Tendon reflexes

6- Hematologic:
Erythropoiesis

7- Reproductive:
Ovulation
Spermatogenesis

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3
Q

What is Hypothyroidism?

A

Low TH

Symptoms:
Slow BMR (Basal Metabolic Rate)
Gain Weight (slow food digestion, feel bloated, store food, slower energy production)
Tired, Fatigue, Lethargic
Constipation
Feeling cold
HR (Heart Rate) slower, (can become Bradycardia)

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4
Q

What is the primary indication for thyroid replacements?

A

Hypothyroidism of any cause.

Symptoms in many body systems

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5
Q

What are the contraindications for thyroid replacements?

A

Caution in conditions where tachycardia is dangerous due to the risk of tachycardia if the dose is too high.

If over supplementation:
Symptoms of Hypothyroidism

Monitor to not cause Hypothyroidism symptoms and Cardiovascular complications or Thyrotoxic Storm

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6
Q

What is the mechanism of thyroid replacement therapy?

A

Exogenous thyroxine replaces deficient endogenous thyroid hormone.

TH binds intracellular nuclear Thyroid Hormone Receptors (THRs) and influence RNA transcription direct. THR has 10 times more affinity to T3 than T4

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7
Q

How does thyroid hormone influence the body?

A

It affects metabolic rate, cardiovascular function, skin and hair composition, GI motility, musculoskeletal system, hematologic system, and reproductive functions.

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8
Q

What are the major forms of thyroid hormone?

A

T4 (thyroxine), T3 (triiodothyronine), and rT3 (reverse T3).

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9
Q

Which thyroid hormone is more active, T3 or T4?

A

T3 is more active, but T4 is more abundant.

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10
Q

Why is T4 preferred over T3 for thyroid replacement?

A

T4 has a longer half-life (once daily) and a lower potential for cardiac toxicity.
Can use T4 alone (or T4 with T3 for endocinology)

T3 has a shorter half-life, it is usually not used alone, instead it is used in combination with T4
Can use T3 only for psychiatry

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11
Q

What are TH Replacement drugs for Hypothyroidism?

A

T4:
Levothyroxine / Synthroid, Levoxyl

T3:
Liothyronine / Cytomel

Levothyroxine is very sensitive when changed, one brand from one manufacturer, if switched to another brand it can cause significant fluctuations in TH levels and lead to symptoms

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12
Q

What medications can decrease thyroid hormone absorption?

A

Bile acid sequestrants, iron, aluminum, and antacids.

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13
Q

How can estrogens affect thyroid hormone response?

A

Estrogens may decrease the response to thyroid hormone.

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14
Q

Which arrhythmia medications’ efficacy can be affected by TH drugs?

A

The efficacy of Beta blockers, Digoxin, and Warfarin can be decreased

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15
Q

When should patient take TH replacement drugs?

A

Levothyroxine should be taken in the morning on an empty stomach

Separated from other med by a few hours (4 hours)

Should take the same dose at the same time

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16
Q

What is the primary method for monitoring thyroid replacement therapy?

A

TSH (thyroid stimulating hormone) levels.

Monitored every 3 months

When adjusting does, do it in increments of 10-25 mcg at 6-8 weeks intervals until TSH levels are in normal range

17
Q

What is the goal of thyroid replacement therapy?

A

To maintain TSH levels within normal limits.

18
Q

What should be done if the dose of thyroid replacement is too high?

A

It can cause symptoms of hyperthyroidism such as weight loss, palpitations, increased appetite, and menstrual irregularities.

19
Q

What is Hyperthyroidism?

A

High TH

High (or fast) BMR
High HR - Tachycardia, Palpitations, Arrhythmias
Lose weight, skinny, don’t gain weight
Feeling hot (related to Tachycardia)

20
Q

What are the two main types of antithyroid treatments?

A

Thioamides - Hyperthyroidism

Radioactive iodine - Hyperthyroidism and Thyroid Cancer (more commonly)

21
Q

What is the indication for thioamides?

A

Hyperthyroidism.

22
Q

What is the indication for radioactive iodine?

A

Hyperthyroidism and thyroid cancer.

23
Q

How do thioamides work?

A

They block the synthesis of thyroid hormone by inhibiting thyroid peroxidase, blocking iodine oxidation, and blocking the coupling of iodinated tyrosines.

Inhibit peripheral deiodination of T3 and T4
Require 3-4 weeks to take effect

24
Q

How does radioactive iodine work?

A

It destroys the thyroid gland via radiation, preferentially targeting the thyroid due to its uptake of iodine.

Half-life is 8 days
Emits primarily Beta Radiation
Penetrates depth of 2 mm

25
Q

What are the contraindications for thioamides?

A

Caution in pregnancy due to placental barrier penetration; avoid use if there was a prior severe reaction.

Routinely monitored and refer to maternal/fetal medicine

26
Q

What are the contraindications for radioactive iodine?

A

Absolute contraindication in pregnancy as it can ablate the fetal gland; pregnancy should be avoided for 6 months after treatment.

27
Q

What are examples of Anti-Thyroids?

A

1- Thioamides:
IMPORTANT:
- Propylthiouracil (PTU)
- Methimazole / Tapazole (most used)

Other:
Carbimazole

2- Ablative Agents:
IMPORTANT:
- Radioactive Iodine (131 I)

28
Q

What are common side effects of thioamides?

A

Common:
Rash, fever, arthralgia.

Rare:
Agranulocytosis (impaired immunity) drug must be stopped
Hepatotoxicity (allergic type response results in liver failure
Vasculitis (autoimmune)

If happens with one Thioamide, 50% will happen with another one

29
Q

What side effects can occur with radioactive iodine?

A

Lifelong need for thyroid replacements, salivary gland inflammation (because of uptake of Iodine), dry mouth, altered taste, dental caries, pain, and a small risk of cancer.

30
Q

How long do thioamides take to exert effects?

A

3-4 weeks.

31
Q

What should be considered when using antithyroid medications?

A

They take 3-4 weeks to lower thyroid hormone levels, so beta blockers may be used initially for symptomatic relief (within hours).

Beta blockers are used for BP and other things that lock Beta receptors, they reduce BP and HR for hyperthyroidism who have high BP and HR

32
Q

How should TSH levels be monitored during antithyroid treatment?

A

Initially monthly, then every 1-3 months once symptoms are under control.

Then can go up to every 6 months, then annually

33
Q

Can hyperthyroidism go into remission?

A

Yes, treatment with thioamides can be used without thyroid ablation or thyroidectomy.

34
Q

How should PCP determine treatment options?

A

1- Hyperthyroidism:
Refer to endocrinologist

2- Hypothyroidism:
Commonly managed and typically not referred to endocrinologist unless significantly out of control or traditional management is not getting it controlled

35
Q

What is Graves’ disease?

A

A condition of generalized diffuse overactivity of the entire thyroid gland, often resulting in a goiter (enlarged thyroid gland) and hyperthyroidism.

36
Q

What is Hashimoto’s thyroiditis?

A

An autoimmune condition where hyperthyroidism can occur before the thyroid gland is destroyed, leading to hypothyroidism.

Symptoms:
First:
Tachycardia
Diarrhea
Difficulty sleeping
Then:
Tiredness
Fatigue
Weakness
Constipation

37
Q

What is myxedema?

A

A severe, life-threatening form of hypothyroidism that can cause death.

Severe and long lasting when Hypothyroidism is left untreated

38
Q

What is cretinism?

A

Severe hypothyroidism in children.

All infants are screened at birth

Marked slowing of growth and development, very serious and permanent consequences

39
Q

What is a thyrotoxic storm?

A

A severe and acute form of hyperthyroidism associated with life-threatening symptoms.

Cardiovascular complications in patient with untreated overactive thyroid

Pharmacology (5 decks)

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