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Pharmacology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Hormone Regulation

A

Bone formation- PTH: calcium, phosphorus
Growth formation- estrogens, androgens: testosterones; GHRH –> GH (Somatropin)
Metabolic rate control- TSH, thyroid hormone (TH)
BP and fluid balance control- cortisol, aldosterone, ADH

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2
Q

Human Growth Hormone

A

Somatropin (genotropin)

  • Recombinant DNA technology is true human factor
  • Stimulates the growth and metabolism of nearly every cell in the body
  • Uses: short stature with or without normal GH levels
  • – Contraindicated in patients with closed epiphyses
  • – Dosing is highly individualized on the basis of child’s growth rate and anticipated trajectory of genetic height
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3
Q

Human Growth Hormone: Pharmacodynamics

A
  • Initially there is insulin-like effect
  • Stimulates growth of linear bones, skeletal muscles, and organs
  • Stimulates erythropoietin
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4
Q

Human Growth Hormone: Pharmacokinetics & ADRs

A

Pharmacokinetics: IM & SC drugs well-absorbed

  • Metabolism: hepatic, renal 90%
  • Excretion: renal

ADRs:

  • Antibody development
  • hyperglycemia, edema
  • hypothyroidism
  • arthralgia, HA, dizziness, flu-like symptoms
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5
Q

Human Growth Hormone: Patient Education & Rational Drug Selection

A

Patient Education

  • Pediatric administration: total weekly dose (0.16 to 0.24 mg/kg) divided in 6-7 doses
  • ADRs
  • Lifestyle management and need to prevent abuse

Rational Drug Selection: Not initiated by NP in primary care practice; work with endocrinologist

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6
Q

Human Growth Hormone: Monitoring

A
  • Hepatic/renal function: before and during treatment

- TSH, glucose, glycohemoglobin, based on symptoms and prior illnesses

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7
Q

Thyroid Hormones: Pharmacodynamics

A

Levothyroxine (T4), Liothyronine (T3), and Liotrix (a 4:1 mixture of T4 & T3)

  • There hormones produce the same effects in the body as endogenous thyroid hormones
  • They also produce a negative feedback loop to reduce further secretion of TSH and thyroid hormones
  • T4 is the drug of choice for thyroid replacement and suppression therapy because of its longer half-life
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8
Q

Thyroid Hormone: Pharmacokinetics

A

Absorption: oral- erratic 40-80%; decreased by age, food, health of GI tract; greater than 99% is protein bound

Metabolism: liver, T4 is converted to T3 in the body; T4 produces both hormones

Excreted: bile/feces

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9
Q

Thyroid Hormone: Precautions & Contraindications

A

Contraindicated after acute MI or thyrotoxicosis
Pregnancy risk factor A, and safe with children
- replacement is advised for all pregnant women
- increased metabolic rate during pregnancy may require higher dosing from baseline
- thyroid hormones are minimally excreted in breast milk
- Children with hypothyroidism need treatment

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10
Q

Thyroid Hormone: ADRs

A

Symptoms of hyperthyroidism:

  • CV: angina, increased BP, flushing, palpitations
  • Central nervous system: anxiety, HA, insomnia

Long-term thyroid replacement associated with decreased bone density in hip/spine in postmenopausal women

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11
Q

Thyroid Hormone: Drug Interactions

A

Bile-acid sequestrants, iron salts, and antacids decrease absorption; estrogens may decrease response

Drugs may decrease action of warfarin, digoxin, and beta blockers

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12
Q

Hypothyroidism: Clinical Treatment

A

Treatment is indicated in patients with TSH levels greater than 10 or in patients with TSH levels between 5 and 10 in conjunction with goiter or positive antithyroid peroxidase antibodies (or both)

Thyroxine replacement is typically lifelong

Consult with pediatric endocrinologist before treating a pediatric patient

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13
Q

T4 Dosing: For patients with no known CV disease

A
  • Initial dose can be started at 50 mcg/day for 2 to 4 weeks and may be increased in increments of 25 mcg/day
  • Average full replacement 100-124 mcg/day
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14
Q

T4 Dosing: For patients 50+ years with CV disease or with long-standing hypothyroidism

A
  • Initial dosing of T4 is 12.5 to 25 mcg/day
  • An increase of 12.5 to 25 mcg increments at approximately 1 month intervals avoids rapid increases in cardiac workload and symptoms of ischemic heart disease
  • If exacerbations of angina pectoris occurs, the previous dosage regimen should be administered and titrated up in smaller increments
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15
Q

T4: Rational Drug Selection

A

T4 is drug of choice for thyroid replacement and suppression therapy

In older adults with no cardiac disease, consider consulting with endocrinologist regarding using T3 or T4 or liotrix

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16
Q

Thyroid Agents: Monitoring

A
  • TSH level should be measured in 6-8 weeks, and the T4 dose should be adjusted as necessary
  • The target TSH level should be between 0.3 and 3.0
  • Once a stable TSH level is achieved, annual examination is appropriate
  • Monitor for osteoporosis in high-risk populations
  • Many drugs affect TSH levels
17
Q

T4: Patient Education

A
  • Take medication each day in the morning, preferably before breakfast because absorption is increased on an empty stomach
  • ADRs: Learn how to measure heart rate
  • Lifestyle management is important
18
Q

Antithyroid Agents: Pharmacodynamics

A

Propylthiouracil (PTU), methimazole (Tapazole)

  • Both block synthesis of T4 and T3
  • Neither drug treats the underlying pathology in hyperthyroidism
  • High relapse rates exist but are less likely if treated for 18-24 months
19
Q

Antithyroid Agents: Pharmacokinetics

A

Absorption: rapidly absorbed after oral dosing, peaking within 1 hours: 85% to 95% bioavailability

PTU is 75% to 80% protein bound; methimazole is NOT protein bound

Both metabolized in the liver; both have short half-life; excreted in urine: 35% of PTU, 80% of methimazole

20
Q

Antithyroid Agents: Precautions, Contraindications, ADRs, & Drug Reaction

A

Precautions & Contraindications

  • Pregnancy major concern: readily cross the placenta
  • – Recommend that patient not get pregnant while on these drugs
  • High concentrations in breast milk
  • PTU not recommended in children

ADRs: agranulocytosis, drowsiness, HA, alopecia, skin rashes, renal/hepatic failure
Drug Reaction: lithium, warfarin

21
Q

Antithyroid Agents: Rational Drug Selection & Monitoring

A

Rational Drug Selection
- Check guidelines, as use in pregnancy and children varies frequently

Monitoring

  • Thyroid studies, CBC, liver/renal panels before starting drug
  • Recheck in 1-2 months after starting drug
22
Q

Antithyroid Agents: Patient Education

A
  • Administration: very important to NOT miss doses; if dose is missed, patient should NOT make up dose
  • Teach about hypothyroid symptoms; prolonged subclinical hyperthyroidism is associated with bone loss, a. fib., and impaired left ventricular diastolic filling
  • Dietary sources of iodine should be reduced because they interfere with action of drugs
  • Watch use of OTC cold medicines
23
Q

Posthyperthyroid Treatment

A

Patients need to expect that they will become hypothyroid

This may not occur for several months

Patients must take thyroid supplements for life

Pharmacology (25 decks)

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