Hypothyroidism
Ambulatory Mini-lecture
December 2014
Background
Hypothalamus = center of homeostasis
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Thyroid releasing hormone (TRH)
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Pituitary
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TSH
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Thyroid
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T4

T3
Thyroid Disorders
TSH
High
Low
T4
Low
Normal
High
Low
Normal
High
Thyroid Status
1⁰ hypothyroid, thyroiditis
Subclinical hypothryoidism
2⁰ (pituitary) hyperthryoidism
2⁰ (pituitary) hypothryoidism
Subclinical hyperthryoidism / ESS / MNG
1⁰ hyperthyroidism, thyroiditis
Hypothyroidism: Causes
• Chronic Autoimmune Thyroiditis
• Amiodarone
• Resolving Subacute Thyroiditis
– Painful: viral, pregnancy, granulomatous
– Silent: postpartum, autoimmune
Hypothyroidism: Symptoms
• Fatigue, weight gain, mental slowness, coarse hair/alopecia,
dry skin, menstrual irregularities, constipation
• Arthralgias, myalgias, headache
• Carpal tunnel and other appendicular neuropathies
• Psychiatric changes
Hypothyroidism: Signs
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•
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Delayed reflexes
Bradycardia
Coarse hair/alopecia
Rare: periorbital and/or non-pitting edema
Hypothyroidism: Other labs
• Anemia
– Normocytic
– Interesting: Pernicious Anemia
• Hyperlipidemia
• Rare: pericardial effusion
• Rare: elevated prolactin ( but still < 100)
Hypothyroidism: Dx
• Magic number = 10
• TSH > 10 + Low T4 = overt hypothyroid
• TSH > 10 + nl T4 = subclinical treat
• TSH 5-10 + nl T4 = subclinical watch
---------------------------------------------------------------• Low TSH + low T4 = central hypothyroid
• Low TSH + low or nl T4 + sick
– euthyroid sick syndrome
Hypothyroidism: Tx
• Think in terms of weeks
– Takes 6 weeks for LT4 to reach steady state
• Start 50-100 ug/day
• Monitor with TSH alone
• Stay in the lower half of normal range
Hypothyroid Take-Home
• Total Body Dolor
• Ten I Shee
• Takes 6 weeks
Hypothyroidism MKSAP
But when Sam Lai leads it, it’s more like a Mix Tape
Question # 1
• A 28-year-old woman is evaluated for a 1-year history of a nonpainful
swelling in her neck. Her health has been otherwise excellent, with no
weight loss, nervousness, or excessive tiredness. She is interested in
becoming pregnant. Her mother and maternal grandmother have thyroid
disease treated with levothyroxine.
• On physical examination, blood pressure is 130/80 mm Hg, pulse rate is
94/min and regular, and respiration rate is 16/min; BMI is 27. Her thyroid
gland is minimally enlarged bilaterally and feels firm. No specific nodules or
cervical lymphadenopathy is palpated. Results of cardiac, pulmonary,
abdominal, and extremity examinations are normal.
LAB VALUES
• Thyroid-stimulating hormone (TSH): 6.5 µU/mL (6.5 mU/L)
• Thyroxine (T4), free: 1.2 ng/dL (15 pmol/L)
• Triiodothyronine (T3), free: 4.0 ng/L (6.1 pmol/L)
• Thyroid peroxidase antibodies: 640 units/L (normal, <20 units/L)
What should be the next step in
management?
1.
2.
3.
4.
FNA of Thyroid Gland
Levothyroxine Therapy
Repeat TSH in 6 weeks
Thyroid Scan
DISCUSSION
• She should receive Levothyroxine therapy
• High risk for overt hypothyroidism, given + FH, + TPO Ab, small goiter and desire to become
pregnant
• Treat patients with TSH levels > 10 microunits/mL, anti-TPO Ab, strong family hx of thyroid
disease, goiter or pregnancy, even if subclinical hypothyroid
• Hypothyroidism in pregnancy is associated with low birth weight, increased risk for miscarriage,
premature birth and fetal loss. TSH goal = 0.5 to 2.5 microunits/mL
• FNA indicated mainly for characterization of nodules
• As she is high risk for hypothyroidism, waiting 6 weeks and then repeating may harm her fetus
• No indication for thyroid scan at this time, such as nodules, or tenderness to the thyroid gland
QUESTION # 2
• A 38-year-old woman reports a 3-month history of increasing fatigue
and weight gain. She underwent transsphenoidal surgery 4 years ago
to remove a nonfunctioning pituitary macroadenoma, followed 4
months later by radiation therapy because of residual tumor. She
started taking hydrocortisone 14 months ago after adrenal
insufficiency was diagnosed. The patient developed amenorrhea 1
year ago and began taking an oral contraceptive. Medications are
hydrocortisone, norethindrone with ethinyl estradiol, and a
multivitamin.
• On physical examination, blood pressure is 102/68 mm Hg, pulse rate
is 64/min, and respiration rate is 12/min. Mild periorbital edema is
noted. The skin is pale.
LAB VALUES
• Hemoglobin = Normal
• Sodium = 134 meq/L
• Prolactin = 22 ng/mL
• TSH = 1.1 microunits/mL
What is the most appropriate next test?
1. Morning serum cortisol measurement
1. Serum free T4 measurement
1. Serum GH measurement
1. Serum LH measurement
DISCUSSION
• She likely has central hypothyroidism, measure free T4
• Hypopituitarism likely 2/2 radiation therapy
• We would expect her TSH to be low with a low free T4
• Her mild hyponatremia may be 2/2 hypothyroidism
• Morning cortisol will be low 2/2 glucocorticoid usage
• GH measurement does not adequately assess GH deficiency, rather,
IGF-1 is the test of choice
• Her LH will also be low 2/2 OCP usage
QUESTION #3
• An 82-year-old man is intubated and admitted to the intensive care unit (ICU) for sepsis
and hypotension from community-acquired pneumonia. According to his wife, the
patient had coronary artery bypass graft surgery 2 years ago and has had intermittent
atrial fibrillation since that time that is treated with amiodarone, 200 mg/d. He has no
history of thyroid abnormalities. Other medications administered in the ICU are
vasopressors, ceftriaxone, and azithromycin.
• Physical examination shows a sedated, ill-appearing older man who is intubated and
cannot respond to questions. Temperature is 37.8 °C (100.0 °F), blood pressure is 90/50
mm Hg (with vasopressors), pulse rate is 110/min and irregular, and respiration rate is
18/min while intubated; BMI is 30. Cardiac examination reveals an irregular rate without
murmurs, rubs, or gallops. Examination of the lungs reveals bibasilar crackles and
rhonchi. The thyroid gland is not palpable. No cervical lymphadenopathy is noted. No
bowel sounds are heard on abdominal examination. The extremities show 2+ peripheral
edema. A few scattered ecchymoses are present on the skin.
LAB VALUES
• Cortisol, random = 28 micrograms/dL
• Thyroid Antibodies = pending
• TSH = 16 microunits/mL
• Free T4 = 0.6 ng/dL
• Free T3, total = 45 ng/dL
• EKG: Tachycardia + Atrial Fibrillation
• CXR: Bibasilar infiltrates
Most likely underlying endocrine disorder?
1. Adrenal Insufficiency
1. Euthyroid Sick Syndrome
1. Hypothyroidism
1. TSH-Secreting Pituitary Tumor
DISCUSSION
• Hypothyroidism
• His extremely high TSH, low T4, and low total T3, along with hx of
Amiodarone usage, point towards hypothyroidism
• He has high cortisol level and an elevated TSH, which is not soley
explained by adrenal insufficiency
• Euthyroid sick syndrome occurs in critically ill patients through an
unknown mechanism.
• But, you would not expect an elevated TSH > 10 microunits/mL
• TSH-secreting tumor would have elevated T4 and T3
QUESTION # 4
• An 88-year-old man is evaluated during a routine physical
examination. He denies any nervousness, weight gain or loss, joint
discomfort, constipation, palpitations, or dyspnea. The patient has a
history of hypertension. Medications are daily lisinopril and daily lowdose aspirin.
• Physical examination shows an alert and oriented older man. Blood
pressure is 140/85 mm Hg; all other vital signs are normal. Cardiac
examination shows a grade 1/6 crescendo-decrescendo systolic
murmur, and pulmonary examination findings are normal. The thyroid
gland is not palpable; no cervical lymphadenopathy is noted. Results
of examination of the extremities, including pulses, are normal.
LAB VALUES
• CBC = Normal
• CMP = Normal
• TSH = 6.8 microunits/mL
• Free T4 = 1.1 ng/dL
• Anti-TPO Ab Titer = Normal
Which is the most appropriate management?
1. Levothyroxine
1. Liothyronine
1. Radioactive Iodine Test
1. Observation
DISCUSSION
• This pt should be observed with repeated tests over the next months
• Normal range of TSH in elderly (> 80 y/o) increased to 1-7
microunits/mL
• Multiple studies show no detrimental medical outcomes with
elevated TSH and, is in fact, associated with lower mortality
• He is asymptomatic and anti-TPO is negative, thus, not requiring T4
• There is no advantage of liothyronine (T3) over T4 and may cause
more cardiac arrhythmias 2/2 short half-life and high spike
• RAI is not utilized in diagnosing hypothyroidism
QUESTION # 5
• A 62-year-old woman is admitted to the hospital in a coma. Her daughter says
that her mother has had progressive lethargy, malaise, disorientation, and ataxia
over the past 2 days. The patient received radioactive iodine therapy 10 years ago
for an overactive thyroid gland and has hypertension. She does not drink alcohol
or smoke. Medications are levothyroxine and hydrochlorothiazide, although the
daughter reports that her mother is only intermittently adherent to her
medication regimen.
• Physical examination shows an ill-appearing woman who is comatose and not
responding to verbal commands. Temperature is 35.9 °C (96.6 °F), blood pressure
is 105/65 mm Hg, pulse rate is 75/min, and respiration rate is 10/min. Cardiac
examination shows a grade 2/6 holosystolic murmur at the left lower sternal
border. Lung examination reveals dependent crackles, but findings are otherwise
normal. The thyroid gland is not palpable, and no cervical lymphadenopathy is
noted. The skin is dry and cold, and the face, lips, and hands are mildly
edematous. Abdominal examination findings are normal.
LAB VALUES
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Leukocytes = 20,000/microliter, with 80% Neutrophils
Sodium = 132
K = 3.5
Cl = 103
Bicarb = 26
Glucose = 45
pH = 7.3
TSH = 140 microunits/mL
Free T4 = 0.2 ng/dL
Total T3 = < 20 ng/dL
Cortisol, Serum = pending
CXR = mild bibasilar infiltrates, enlarged heart. CT Head = normal
What is the most appropriate treatment?
1. IV Levothyroxine
1. IV Levothyroxine and Hydrocortisone
1. IV Liothyronine
1. IV Liothyronine and Hydrocortisone
DISCUSSION
• This myxedema coma pt should receive Levothyroxine +
Hydrocortisone
• Myxedema Coma = hypo-tension, -glycemia, -thermia, bradycardia
• Levothyroxine bolus of 200-500 mcg, then 50-100 mcg IV daily
• May cause cardiac irregularities
• Myxedema coma may also be associated with other pituitary
abnormalities, thus, steroids should also be administered
• Pt should also be checked for adrenal insufficiency
• Liothyronine usage is controversial, no definitive benefit shown