Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

3152 > thyroid > Flashcards

thyroid Flashcards

1
Q

Thyroid gland

A

○ Endocrine gland (secrete hormones directly into bloodstream)
○ Located in middle of lower neck
○ “butterfly” shape

Releases THYROID HORMONE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

TH regulates

A

Regulate body physiological functions
Relate to development, growth, metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

physiological functions of thyroid hormone

A

body temp
CNS
sleep
cardiac
GIT
muscle strength
breathing
menstrual cycle
skin dryness
lipid metabolism
ulitlisation of glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Mechanisms negative feedback

A

1) Hypothalamus detect circulating TH low
a) Hypothalamus release thyrotropin-releasing hormone (TRH)
2) TRH instruct pituitary to release TSH
3) TSH instruct thyroid gland to secrete TH
4) Elevated lvl of circulating TH in blood
a) Hypothalamus sense incr in TH, stop release of TRH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

TSH is ___ in 1* hypothroidism

A

ELEVATED

  • Hypothalamus detect persistently low lvl of TH
    ◊ Hypothalamus secretes TRH
  • Instruct pituitary to secrete TSH
  • Unsuccessfully stimulate thyroid gland to secrete TH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

TSH is ___ in 1* hyperthroidism

A

LOW

-Hypothalamus detect persistently high lvl of TH
◊ Hypothalamus STOP secrete TRH
- No instruct pituitary to secrete TSH
- Independently functioning thyroid gland that continues to secrete TH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

TH exists in

A

4:1 ratio (T4:T3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

T3 is

A

more potent

◊ 80% of T3 is peripheral converted from T4
◊ T1/2 of 2 days
◊ 99% protein bound
Not routinely ordered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

T4 is

A

◊ T1/2 of 6-7 days
◊ 99% protein bound
- FreeT4 unbound (that carry out metabolic effect), routinely ordered with TSH – evaluate thyroid stores in pt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is needed for TH

A

idoine (Obtained exogenously), thyroglobulin, tyrosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Peripheral conversion – TBG

A

§ 80% of T3 is peripheral converted from T4

§ Affected by binding to proteins
□ Eg: pregnant (elevated TBG - thyroxine binding globulin)
- Decr T3, T4 (free unbound), more bound to extra TBG
- TSH released. Instruct thyroid gland release more THs for FT3, FT4 to normal

                     * Risk hypothyroidism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

test for autoimmunity

A

1) antibodies
(ATgA, TPO, TRAb)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

ATgA

A

thyroglobulin Ab

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

TPO

A

thyroperoxidase Ab (sig associated with hypothyroidism)

□ 95% of pt Hashimoto (inflammation): ATgA + TPO
□ 60-70% Graves (hyperthy): ATgA + TPO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

TRAb

A

thyrotropin receptor IgG Ab
□ Specific, confirmatory for Graves
□Expensive test

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

ranges

A

T4 = 0.8-2.7

TSH = 0.4 - 4.2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When to screen:

APR Li RS

A

1) Presence of autoimmune disease (T1DM, cystic fibrosis)

2) 1st degree relative w/ autoimmune thyroid disease (genetics)

3) Psychiatric disorders
a) TH abnormality affects psychiatric

4) Take amiodarone/ lithium

5) History of head/ neck radiation for malignancies
a) Radiation predisposes

6) Symptoms of hypo/ hyperthyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

ROUTINE TEST FOR ONLY

A

(risk developmental risk)

1) Preg
2) Pediatric pt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

hypothyroidism

A

TSH Elevated in 1* hypothyroidism
- Hypothalamus detect persistently low lvl of TH
◊ Hypothalamus secretes TRH
- Instruct pituitary to secrete TSH
-Unsuccessfully stimulate thyroid gland to secrete TH

HIGH TSH, LOW TH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

1* hypothroidis:

A
  • Iodine deficiency **
  • Hashimoto disease
    ○ If no iodine insuff
    ○ Chronic autoimmune thyroiditis
  • Iatrogenic
    ○ Thyroid resection for HYPER
    ○ Radiation ablative therapy for HYPER
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

2nd causes of hypothyroidism

A
  • Central hypothyroidism
    Not thyroid gland issue
    ○ Hypothalamus unable to secrete TRH
    ○ Pituitary unable to secrete TSH
  • Drug induced
    ○ Amiodarone, Li
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

hypothyroidism Signs and symptoms

A

Cold intolerance
Dry skin
Fatigue, lethargy, weak
Weight gain
Bradycardia
Slow reflex
Coarse skin, hair
Periorbital swelling
Menstrual disturbances (more freq, more blood)
- Less thyroid, less estrogen, progestin
- More painful cramps
Goiter
- Enlarged thyroid gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

hypothyroidism Clinical manifestations

A
  • HIGH total cholesterol, LDL, TG
    • HIGH atherosclerosis, MI risk
  • HIGH creatine phosphokinase (CPK) lvls
    • DDI statins (will cause CPK to rise too)
  • Incr miscarriage risk
    *Impaired fetal development
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Diagnosis for hypothyroidism

A

1) Signs and symptoms
2) Labs

- hypothyroidism (thyroid gland issue) 
	* HIGH TSH, LOW T4
	* +ve Ab (TPO, ATgA) 

- Central hypothyroidism (pituitary gland issue) 
	* LOW TSH, LOW T4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Goals of therapy for hypothyroidism

A
  • Eliminate symptoms, improve QOL
  • Minimise LT damage to organs
    • Myxedema coma
    • Heart Disease
  • Prevent neurologic deficits in newborns, children
  • Normalise FT4, TSH conc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

2 drugs for hypothyroidism

A

Levothyroxine (synthetic T4 )
Liothyronine (synthetic T3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

dose of levothyroxine

A

a. Young, healthy adults: 1.5-1.6 mcg/kg/d
b. 50-60 yrs (no CVS): 50mcg daily
c. 50-60 yrs (w/ CVS): 12.5 - 25 mcg/d
i. Titrate up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

admin of levothyroxine

A
  • 30-60mins before bfast
  • 4hrs after dinner (empty stomach)
    ○ For meals, meds
  • If Ca/ Fe suppl/ antacids/ milk
    ○ Space 2 hrs apart
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

titrate levothyroxine

A

a. Response
i. Control of symptoms
ii. Normalisation of TSH, T4

b. Incr/ decr by 12.5-25 mcg/ day increments
c. Incr/ decr by 10-15% of wkly dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Monitor levothyroxine

A
  • 2-3mnths assess response in TSH (after start/ change in therapy)
    ○ Target TSH: 0.4-4mIU/L (WNL)
    ○ Symptomatic relief (within 2-3wks)
    § Negative feedback takes time to regulate (TSH, T4 to normal)
    *euthyroid state: TFT semiannual - annually in non preg
  • Normal FT4 + HIGH TSH
    ○ = non-adherence
  • If central hypo (use FT4, no TSH)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

ADR/ sign of over replacement of T4

A
  • Cardiac abnormalities
    ○ Techy, angina, MI
  • Risk of fractures
  • Signs of hyperthyroidism
32
Q

Liothyronine, synthetic T3

A

T1/2 = 1-2.5 days (much shorter than T4)

33
Q

Liothyronine ADR

A
  • High risk of ADR
    ○ Not recc
34
Q

when liothyronine is used

A

1) Combi T3, T4 — if normal TSH, but still symptoms of hypothyroidism
2) Myxedema coma — Very low TH, in coma
3) diagnostic criteria, CT scan, contrast media exposure

§ Stop T4, put on T3, stop 1-2 days before
§ Shorter t1/2

35
Q

Monitoring hypothyroidism

A
  • Upper limit normal of TSH in older adults continue to rise
    • Age-related shift
    • Adults > 70 yrs (TSH ~ 6.9mIU/L)
  • After euthyroid state achieved
    • TFT recc semiannually –> annually in nonpreg adults
36
Q

Hypothyroidism & preg EFFECTS

A
  • Miscarriage, spontaneous abortion
  • Congenital defects, impaired cognitive development
    • Maternal TH provide fetus with TH for up to 6wks
      Until fetus forms own thyroid gland
37
Q

mother alr on levo before preg

A

○ Incr dose 30-50% in pre-preg dose
- To maintain euthyroid status: incr in thyroid binding proteins

* Target TSH:
	1) Trimester: <2.5mIU/L
	2) Trimester: <3.0mIU/L
	3)Trimester: <3.5 mIU/L
38
Q

Subclinical hypothyroidism (early stage)

A
  • HIGH TSH, normal T4 –> early Hashimoto disease
  • Risk:
    ○ TSH > 7.0mIU/L
    § Older adults = risk of HF
    ○ TSH > 10mIU/L
    §Risk of coronary HD
39
Q

Treatment for subclinical hypothyroidism??

A

(may risk incr TSH further, incr HF risk) ONLY TREAT:
○ TSH > 10mIU/L
○ TSH 4.5 - 10mIU/L
-Symptoms of hypothyroidism?
- TPO present
- Hist of CVS, HF, risk factors (genetics)

Start with: 25-75mg

If left untreated, screen regularly for development of OVERT hypothyroidism [HIGH TSH, LOW T4]

40
Q

hyperthyroidism definition

A

TSH low lvl in 1* hyperthyroidism
- Hypothalamus detect persistently high lvl of TH
◊ Hypothalamus STOP secrete TRH
- No instruct pituitary to secrete TSH
- Independently functioning thyroid gland that continue to secrete TH

LOW TSH, HIGH TH

41
Q

cause of hyperthyroidism

A
  • Toxic diffuse goiter (GRAVES disease)**
    ○ Thyroid receptor Ab (TRAb) mimics TSH
    ○ Stimulate TH production
  • Pituitary adenomas
  • Toxic adenomas (HOT NODULE)
    ○ Singular nodule
    ○ Oversecrete TSH –> T4
  • Toxic multi-nodular goiter (Plummer’s disease)
    ○ Multi nodules that secrete T3
  • Drugs induced
    ○ Amiodarone, Li
  • Subacute thyroiditis
    ○ Infections/ drug induced
    ○ Early HASHIMOTO’s disease
    ○ Release of STORED hormone
    - HYPER –> HYPO (after explode)
42
Q

signs and sx of hyperthyroidism

A

Weight loss, incr appetite
heat intolerance
Goiter
Fine hair
Heat palpitations/ tachycardia
Nervousness, anxiety, insomnia
Menstrual disturbances
(lighter/ infreq menstraution/ none)
Sweating, moist, warm skin
Exophthalmos (graves): bulging eyes (oedema, cytokines promote inflam)

43
Q

Diagnosis of hyperthyroidism

A
  • Signs and symptoms
  • HIGH FREE T4
  • LOW TSH (except in TSH-secreting adenomas)
  • RAIU (radioactive iodine uptake)
    • Used to better see if the gland is ACTIVELY secreting TH
    • INCR UPTAKE:
      ○ Graves, TSH-secreting adenomas, toxic adenoma, multinodular goiter
    • DECR UPTAKE:
      ○ Thyroiditis, cancer
  • Presence of TRAb, ATgA, TPO
    *Biopsy
44
Q

goals of treating hyperthyroidism

A
  • Minimise/ eliminate symptoms, improve QOL
  • Minimise LT damage to organs
    • Heart disease, arrhythmias, cardiac death, bone demineralization, fractures
  • Normalise free T4, TSH conc
45
Q

non pharm therapy of hyperthyroidism

A

1) Surgical resection
- Causes hypothyroidism
- Cut out part
2) Radioactive iodine (RAI)
- Ablative therapy
- Conc in thyroid tissue
- Destroys overactive thyroid cells
-Preg is CI
3) Thyroidectomy
- Complete removal
- Results in hypothyroidism

46
Q

Antithyroid pharmacotherapy (hyperthyroidism) used in which pop

A

1) Those awaiting ablative/ surgical resection
* Depletes stored T4, T3
*Minimise risk of post-ablation hyperthyroidism caused by thyroiditis

2) Pt that cannot undergo ablation (not candidates) // failed to normalise thyroid
○ Preg, old, young
○ Cannot go radiation therapy
○ leave radioactive reminants

3) Mild disease/ small goiter/ low or neg Ab titers/ women

4) Limited life expectancy too old

NOT LONG TERM

47
Q

eg of antithyroid pharm

A

Thionamides (carbimazole & propylthiouracil)

Iodides

Non-selective beta blockers (propanolol)

48
Q

Thionamides (carbimazole & propylthiouracil)

A

Inhibit iodination and synthesis of TH

i. PTU blocks T4/T3 conversion in periphery at high dose

49
Q

Thionamides dose

A

i. PTU: 50-150mg TDS
1) Euthyroid: reduce to 50mg BD/ TDS

ii. Carbi: 15-60mg daily (split BD/ TDS)
1) Euthyroid: reduce to 5-15 mg OD

50
Q

Thionamides ADR

A

i. Hepatotoxic risk *PTU
ii. Rash, SJS
iii. Agranulocytosis (early therapy, 3mnths)
iv. Fever

51
Q

Efficacy of thionamides

A

i. Slow onset in reducing symptoms, max effect 4-6mnths

ii. Remission rates is low (20-30%)
1) Normal TSH, T4 for 1 yr after stop antithyroid therapy

iii. Monthly dose titration
1) Based on symptoms, FT4
2)TSH remain supp for mnths, FT3, FT4 better markers

52
Q

Iodides MOA

Lugol’s sol (sat sol of KI)

A

inhibit release of stored TH

Minimal effect on hormone synthesis

Decr vascularity and size of gland

53
Q

place in therapy of iodides

A

i. Before surgery (7-10 days) = shrink
ii. After ablation (3-7days) = inhibit thyroiditis mediated release of stored TH (BURST)
iii. Thyroid storm (too much TH)

54
Q

considerations when using iodides

A

i. Limited efficacy after 7-14 days of therapy. TH release will resume

ii. NOT BEFORE ablative RAI (reduce uptake of radioactive I-)

55
Q

Non-selective beta blockers – propanolol MOA

A

block hyperthyroidism manifestations mediated by b-adrenergic receptors
Block T4 conversion –> T3 (at high dose)

56
Q

propanolol Place in therapy:

A

i. SYMPTOMATIC RELIEF
ii. Bridge for thionamides effect to kick in, before ablation, surgery
iii. PRN for high risk pt (elderly + CVS)
Treatment of thyroiditis (self-limit)

57
Q

preg and hyperthyroidism sx

A
  • Failure to gain weight, despite good appetite
  • Tachycardia
  • Fetal loss if untreated
    but if use Thionamides: risk of embryopathy
58
Q

tx for preg + hyperthyroidism

A
  • Lowest dose
  • Keep T4 at upper-normal limit
  • 1st trimester:
    ○ Impt organs formation
    ○ Use PTU > carbi (Risk of congenital malformation)
  • 2nd, 3rd trimester:
    ○ Use Carbi > PTU (Risk of hepatotoxic, also less potent)
59
Q

Subclinical hyperthyroidism

A
  • Definition: low/ undetectable TSH + normal T4
  • Risk:
    ○ Incr risk of AF (pt > 60yrs)
    ○ Incr risk of bone fracture (Post menopausal women)

Conflict data about mortality risk

60
Q

Subclinical hyperthyroidism tx

A

○ Overt hyperthyroidism except ORAL therapy alternative > to ablative
§ In young patients
○ TSH <0.10mIU/L
○ BB if AF

Untreated: screen regularly for development of overt hyperthyroidism (LOW TSH, HIGH T4)

61
Q

Drug induced thyroid disease 3 eg

A

Amiodarone
lithium
interferon alfa

62
Q

Amiodarone

A

○ Contains iodine in chemical structure
○ Affects iodine uptake, secretion, production —> thyroiditis

HYPO/ HYPER

63
Q

lithium

A

○ Inhibit TH secretion, release
○ Signal incr TSH –> goiter development (due to hypo)
○ leads to HYPER thyroiditis

64
Q
  • Interferon alfa
A

○ Thyroiditis (HYPER then HYPO)

65
Q

Carbimazole MOA

A

1) Inhibit thyroid peroxidase
- Iodinates tyrosyl residues in thyroglobulin
- For T3,T4

2) Reduce synthesis of thyroid hormones

66
Q

carbimazole function

A
  • Inhibit thyroid hormone synthesis
  • Gradual decr thyroid hormones (T3,4) output
    • Reduce signs & sx of thyrotoxicosis
  • Hyperthyroidism
  • Control disease before surgery
    • Excised part of enlarged thyroid gland
  • Clinical response: takes 3-6wks
    • T4 long half life
      • Thyroid stores to deplete
67
Q

carbimazole PK

A

A: PO
- OD dosing
- converted to active methimazole in serum (after absorption)

D: clinical effect lasts a day – concentrated in thyroid
(methimazole: T1/2 ~ 4-6hr)
* No bind to plasma proteins
* Produce 90% inhibition of thyroid organification of iodine within 12hr

M: liver – CYP450, FMO enzyme
- oxidation of xeno-substrates

E: 90% excreted in urine. 10% feces

68
Q

ADR of carbimazole

A
  • Rashes
  • Joint pain
  • N
  • Jaundice
  • Agranulocytosis (rare)
  • Hypothyroidism (over treat)

Monitor: thyroid size, TSH levels (to normal levels)

69
Q

CI of carbimazole

A
  • Liver insuff
  • Prevent hypothyroidism
70
Q

levothyroxine MOA

A

Synthetic thyroid hormone (T4)

1) Taken up by cell 
2) De-iodination to active T3
3) Hormone enter nuclues
	a. Affect metabolic pathway in body 
4) Incr protein synthesis for
           a.  Proteins, enzymes, pumps that incr T3,T4 levels in blood
71
Q

levothyroxine function

A
  • Restore body normal lvl of T4

Special case: myxoedema coma
* Severe form of hypothyroidism
* Reduce blood flow
* Affect gut absorption of LEVOTHYROXINE

  • IV Liothyroxine (synthetic T3)/ IV levothyroxine used
72
Q

PK of levothyroxine

A

A: PO (empty stomach with water. 30min before meal)
- erratic is dietary fibre (affect absorption)

F~ 70-80%

D: T1/2 ~ 7days (OD dose)
* 99% High bind to plasma proteins

M: deiodination site (T4–>T3)
* Main: LIVER
○ Also phase 2: Glucuronidation, sulphation
* Kidney, peripheral

E: feces, urine
Bile – metabolites

73
Q

levothyroxine F affected by

A

Mainly absorbed in duodenum, jejunum (affected by gastric pH)
- antacids, PPI decr

74
Q

ADR of levothyroxine

A
  • LOA
  • ANX
  • Diarrhea
  • Difficulty sleeping
  • Hair loss

Serious:
* Heart issues
○ Arrhy, high
* BP, pain, HF
Seizures

75
Q

monitor for levothyroxine

A
  1. Serum TSH measure to monitor adequate treatment
  2. TSH measure 2-3mnths after initiation// change dose
  3. If TSH persistently high
    a. Inadequate dose
    b. Poor compliance
    c. Malabsorption
    d. Drug/ food interaction
76
Q

CI for levothyroxine

A
  • pH
  • absorption
  • GI motility
  • plasma protein binding
  • liver enzyme (induce/ inhibit)
    Food
  • Fiber
  • Grapefruit
  • Pomelo

FIBRE, antacids, PPI decr absorption

3152 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions