Thyroid Disorders - Scholting Flashcards
What thyroid hormone is the major product of the thyroid gland?
T4
What thyroid hormone is active at the cellular level?
T3
biologically more active; shorter half life
Primary hypothyroidism affects what level?
Gland
Secondary hypothyroidism affects what level?
Pituitary
Tertiary hypothryoidism affects what level?
Hypothalamus
Describe the hypothalamic-pituitary-thyroid axis:
Hypothalamus releases TRH which stimulates pituitary. Pituitary releases TSH which acts on the thyroid. Thyroid hormones then exhibit NEGATIVE feedback on the pituitary and hypothalamus.
Describe the spectrum of presentation of hypothyroidism (3).
- Subclinical hypothyroidism (elevated TSH, normal T4)
- Symptomatic disease
- Severe myxedema coma
Etiologies of Primary Hypothyroidism (9)
- Autoimmune (Hashimotos)
- Idiopathic
- Post ablation
- Post external radiation
- Thyroiditis (subacute, silent, postpartum)
- Infiltrative Disease (lymphoma, sacroid, amyloidosis, Tuberculosis)
- Congenital
- Iodine Deficiency
- Drug-induced hypothyroidism (Amiodarone, lithium)
Etiologies of Secondary Hypothyroidism (3)
caused by insults to the pituitary gland
- Neoplasm
- Infiltrative
- Hemorrhage into the gland
Etiologies of Tertiary Hypothyroidism (4)
- Neoplasm
- Infiltrative Disease
- Anorexia Nervosa
- Cerebrovascular or surgical insult
What causes systemic symptoms of hypothyroidism?
lack of T3
Frequent Signs and Symptoms of Hypothyroidism
all of the signs and symptoms are listed
Weakness Edema of face Lethargy Course Skin Slow Movements Edema of Eyelids Sensation of Cold Hoarseness Peripheral Edema Dry Skin Decreased Sweating Pallor of Lips Slow speech Cold Skin Constipation Thick Tongue Paresthesias Gain in weight Muscle Weakness Slow cerebration
Typical Symptoms of Hypothyroidism (6)
fatigue weakness cold intolerance constipation weight gain deepening of voice
Cutaneous Symptoms of Hypothyroidism (4)
dry, scaly, yellow skin
non-pitting waxy edema of the face
myxedema
thinning of eyebrows
Cardiac Symptoms (3)
bradycardia
enlarged heart
low voltage electrocardiogram
Hypothyroidism Symptoms in the Neck (5)
Pain Swelling Tenderness Nodules Cysts or could be asymptomatic
Neurological Symptoms of Hypothyroidism (3)
Paresthesia
Ataxia
Prolongation of DTR
Describe the hormone levels in HYPOthyroidism - TSH and T4
TSH: increased (normal 0.5-5.0 ug/mL)
Free T4: low or low-normal (normal 0.7-1.86 ng/dL)
thyroid is unable to produce sufficient quantities of hormone (low T4), so pituitary compensates further stimulating the thyroid (high TSH)
What is Hashimoto’s Disease?
What markers will be present?
Autoimmune thyroiditis
Positive test for antibodies - Anti-Tg and Anti-TPO
10 x more common in women
What is subclinical hypothyroidism? How is it treated?
Elevated TSH with normal free T4
TSH > 10: treat
TSH 5-10: monitor or possible trial of hormone replacement
What is Acquired Transient Central Hypothyroidism also known as Euthyroid Sick Syndrome?
Extremely ill patients with non thyroidal illness
Euthyroid with elevated TSH but normal free T4
It generally resolves without treatment, only treat if TSH > 10
What is Goiter?
Enlargement of Gland
can be uniform or diffuse; irregular or multi nodular
How is goiter managed?
- Suppression Therapy: thyroid hormone replacement, decreases TSH stimulation
- Rapidly enlarging - biopsy
- If hypo or hyper treat for the condition
Diagnostic Testing: Serum TSH
Primary Hypothyroidism Primary Hyperthyroidism (over-replacement of hypothyroid state)
Diagnostic Testing: Serum Free Thyroixine (FT4)
Estimates unbound (free) T4 HIGH = HYPER LOW = HYPO
Diagnostic Testing: Total Thyroxine
thyroxine is protein bound - drugs and conditions can alter the level
HIGH = HYPER
LOW = HYPO
Diagnostic Testing: Total and Free T3
useful for diagnosing HYPERthyroidism
Diagnostic Testing: Thyroglobulin
papillary or follicular thyroid cancer
may indicate: recurrent tumor
Diagnostic Testing: Thyroid Antibodies
autoimmune conditions
HYPO: Hashimotos
HYPER: Graves
What thyroid diagnostic test should you order first in an asymptomatic patient?
TSH initially
if HIGH - T4 to confirm HYPO
if LOW - T4 and total T3 HYPER
What is thyroid diagnostic test should you order first in a symptomatic patient or patient with risk factors?
Both TSH and free T4
Lab Abnormalities in Hypothyroid Conditions: LIPIDS
increased triglycerides and cholesterol
normalizes with treatment
Lab Abnormalities in Hypothyroid Conditions: Cellular Enzyme Elevation
CK - suggests myopathy
AST and LDH
normalizes with treatment
Lab Abnormalities in Hypothyroid Conditions: Hyponatremia
associated with SIADH
normalizes with treatment
Which patients should be screened for thyroid disorders?
Patients with: Atrial fibrillation, Osteoporosis, Hyperlipidemia, Diabetes Mellitus, Down or Turner’s Syndrome
Patients Taking: Amiodarone or Lithium
Radioactive Iodine Uptake Imaging
I131
Used for the evaluation of Nodules
“Hot” less likely to be malignant
RAIU - Increased Uptake
Grave’s Disease
RAIU - Decreased Uptake
Silent thyroiditis
Subacute thyroiditis
Postpartum thyroiditis
Exogenous hyperthyroidism
RAIU - What does hot nodule and cold nodule mean?
Hot - take up iodine - overactive; can overproduce thyroid hormone
Cold - under active thyroid
Thyroid Ultrasound Uses
following nodules
determine character of nodule
guidance of fine-needle aspiration
drugs that decrease TSH secretion (low serum TSH)
Dopamine
Glucocorticoids
drugs that INCREASE thyroid hormone secretion
Iodine
Amiodarone
drugs that DECREASE thyroid hormone secretion
Lithium
Iodine
Amiodarone
drugs that DECREASE T4 absorption
Ferrous Sulfate
drugs that INCREASE TBG concentration
Estrogens
Management of Hypothyroidism
Lifelong replacement therapy
Autoimmune causes - removal or ablation
Drug for Thyroid Replacement Therapy and Goal of Treatment
Levothyroxine - stay with same brand (bioequivalency issues)
goal: normalize TSH (0.4-2.0 mIU/L)
over-replacement if <0.3 risk osteoporosis and atrial fibrillation
6-8 weeks to stabilize; once stable check every 6 months to yearly
Thyroid Replacement for Healthy Patients
full dose
1.6 ug/kg/day
reassess TSH in 6-8 weeks
Thyroid Replacement in Elderly Patients or those with Cardiac Disease
start low and go slow
Signs and Symptoms of Hyperthyroidism
Goiter Sweating of hands Weight loss Tiredness Palpitations Regular Pulse > 90 Lid Lag Dyspnea on Exertion Finger Tremor Nervousness Excessive Sweating Hot Hands Preference for Cold Exopthalmos Hyperkinesis Diarrhea Scant Menses Atrial Fibrillation
What is Apathetic Hyperthyroidism?
elderly patients present with minimal symptomology of hyperthyroidism
Signs and Symptoms of Graves Disease
Diffuse Nontoxic Goiter
Ophthalmopathy: stare, lid lag, exopthalamos
Dermopathy - pretibial myxedema
Thyroid Acropachy - digital clubbing, periosteal reaction
Causes of Hyperthyroidism
Graves Toxic Multinodular Goiter Thyroid Nodule Thyroiditis Exogenous intake Medications: Amiodarone; iodine RARE: adenoma, trophoblastic disease, stuma ovarii
Complications of Hyperthyroidism
Very distressing
Atrial Fibrillation
CHF, Angina, MI, Sudden Death
Osteoporosis
Hyperthyroidism Treatments
Radioiodine ablative therapy
Sub-total thyroidectomy
Antithyroid drugs
Symptom treatments
Radioiodine Ablative Therapy
most common treatment for Graves
goal of treatment: Hypothyroidism
Sub-total Thyroidectomy
goal: leave enough gland to produce endogenous hormone
spare: parathyroid glands, recurrent laryngeal nerves
Antithyroid Drugs
Propythiomuracil (PTU) and Methimazole
decrease the production of thyroid hormones - important to monitor hormone levels
preferred in pregnant patients
side effects: agranulocytosis
seek immediate care for fever or sore throat
Symptomatic Treatment of Hyperthyroidism
B-Blockers: tremor and heart rate
Diltiazem & Verapamil
Clonidine
** used until definitive treatment completed
What is Thyroid Storm?
Sudden severe exacerbation of thyrotoxicosis
often precipitated by trauma, infection, surgery
Symptoms of Thyroid Storm
fever
severe tachycardia
delirium
Treatment of Thyroid Storm
antithyroid drugs: PTU or methimazole
high dose glucocorticoids
potassium iodide to suppress further hormone release
Thyroid Nodule Risks for Malignancy
prior radiation
< 30 years of age; > 60
family history
Evaluation of Thyroid Nodule
TSH, Free T4 and T3
Normal TSH: fine needle aspiration
Benign: follow clinically
Malignant: surgical referral
Multinodular Goiter
diffuse process
identified on physical exam
low risk of malignancy
Subacute Thyroiditis
cause: postviral
s&s: anterior neck pain; elevated ESR
tx: symptomatic - analgesics
typically recover euthyroid
Painless Thyroiditis
autoimmune - leads to long term hypothyroidism no neck discomfort decreased uptake of radio iodine postpartum: w/in 1 year of delivery silent: not associated w/ childbirth
FOUR Phases of Thyroiditis
Hyperthyroid
Euthyroid
Hypothyroid
Some recover to a euthyroid state
