Download Thyroid Disorders

Thyroid Disorders
in Primary Care
Dawn O’Reilly, Ph.D., MMS, PA-C
August 25th, 2016
NCAPA Summer Conference
Disclosure
I have nothing to disclose during this presentation.
Objectives
1.Explain the normal anatomy and regulation of thyroid
function
2. Discuss the evaluation of patients with thyroid
disorders
3. Describe the expected changes in TSH and thyroid
hormone levels in patients with thyroid disorders
4. Define the treatment options for thyroid disorders
Patient Case
31yo female patient presents to your office with chief
complaints of feeling tired and she is always cold. She
said that she has been stressed lately with just starting
as a new PA in family medicine, being a police wife,
and her one year old son. She just assumed this is why
she is always tired. She said her husband is also very
annoyed that she always has cold hands and feet and
needs the heat on when its 80 degrees. She would like
to plan to have another child soon. She lives a very
active lifestyle, exercises daily, and eats healthy most
of the time.
Allergies: None
Current Medications: Prenatal Vitamins
PMH: None
Surgical History: L4 fixation 2002, L4/L5 fusion 2006
FH: Hypertension, Hyperlipidemia
Vitals: BP: 118/68, HR: 65, Temp: 98.8, R: 16
Where does the Thyroid Function all Begin?
• The thyroid gland is part of the neuroendocrine system.
• The Hypothalamus is the major integrating
link between these systems and receives input
and controls the pituitary gland with 9
different releasing and inhibiting hormones.
• It regulates virtually all aspects of growth,
development, metabolism, and
homeostasis.
Endocrine glands: secrete products(hormones) into
the bloodstream(pituitary, thyroid, parathyroid,
adrenal)
Exocrine glands: secrete products into ducts which
empty into body cavities or body surface(sweat, oil,
mucous and digestive)
Where does the Thyroid Function all Begin?
• The hypothalamus regulates
thyrotroph cells which produce
TRH(thyrotropin-releasing
hormone) which then stimulates
the ANTERIOR pituitary gland to
produce TSH(thyroid stimulating
hormone)
• TSH stimulates virtually all
aspects of thyroid follicular cell
activity!
The Thyroid Gland
•
The thyroid consists of the thyroid
follicles composed of follicular cells,
which secrete the thyroid hormones
thyroxine(T4) and
triiodothyronine(T3), and
parafollicular cells, which secrete
calcitonin(CT).
Did You Know?
The Thyroid Gland is the ONLY endocrine gland
that stores its secretory product in large
quantities-normally about a 100-day supply?!
So How Does it Do
All That?!
Thyroid Hormone Synthesis:
The formation, storage, and release steps
include:
1. iodide trapping
2. synthesis of thyroglobulin
3. oxidation of iodide
4. iodination of tyrosine
5. coupling of T1 and T2
6. pinocytosis and digestion of colloid
7. secretion of thyroid hormones(T3 and T4),
and transport to the blood
What is the role of Thyroid Hormones?
T3&T4: responsible for
metabolic rate, synthesis of
protein, breakdown of fats,
use of glucose for ATP
production
Calcitonin: responsible for
building of bone and stops
reabsorption of bone
(lowers blood levels of
Calcium)
Negative Feedback System
Where is TSH produced?
A. Hypothalamus
B. Anterior Pituitary Gland
C. Posterior Pituitary Gland
D. Thyroid Gland
Where is TSH produced?
A. Hypothalamus
B. Anterior Pituitary Gland
C. Posterior Pituitary Gland
D. Thyroid Gland
What is the role of the Thyroid Gland?
A. Regulate Oxygen and Basal Metabolic Rate
B. Cellular Metabolism
C. Growth and Development
D. All of the Above
What is the role of the Thyroid Gland?
A. Regulate Oxygen and Basal Metabolic Rate
B. Cellular Metabolism
C. Growth and Development
D. All of the Above
What happens when
the thyroid gland doesn’t work?
• 0.1-2.0% of American adults have overt hypothyroidism
and 4-10% have subclinical hypothyroidism
• 1.3% have hyperthyroidism
• Thyroid dysfunction is 5x higher in woman
• Framingham Study: Clinically apparent thyroid nodules
were present in 6.4% of women and 1.5% of men
• 37-57% of patients had thyroid nodules in autopsy surveys
Who should be checked for hypothyroidism?
• Anyone with symptoms that could be consistent with
hypothyroidism
• Anyone with laboratory or radiologic abnormalities
• Patients with risk factors for hypothyroidism (ex: h/o
autoimmune diseases or family history of autoimmune
thyroiditis)
• Patients who take drugs that can impair thyroid function
• Women who are trying to become pregnant or already
pregnant
Patient Case
31yo female patient presents to your office with chief complaints
of feeling tired and she is always cold. She said that she has been
stressed lately with just starting as a new PA, being a police wife,
and her one year old son. She just assumed this is why she is
always tired but wanted to make sure. She said her husband is
also very annoyed that she always has cold hands and feet and
needs the heat on when its 80 degrees. She would like to plan to
have another child soon. She lives a very active lifestyle, exercises
daily, and eats healthy most of the time.
Allergies: None
Current Medications: Prenatal Vitamins
PMH: None
Surgical History: L4 fixation 2002, L4/L5 fusion 2006
FH: Hypertension, Hyperlipidemia
Vitals: BP: 118/68, HR: 65, Temp: 98.8, R: 16
What kind of physical exam would you pay
attention to?
A comprehensive physical exam
should be performed
• Weight and blood pressure
• Pulse rate and cardiac rhythm
• Thyroid palpation and auscultation(to
determine thyroid size, nodularity, and
vascularity)
• Neuromuscular examination
• Eye examination (to detect evidence of
exophthalmos or opthalmopathy)
• Dermatologic examination
• Cardiovascular examination
• Lymphatic examination (nodes and spleen)
Patient Case
General: Well Developed, Well Nourished, No
distress,
Head, Eyes, Ears, Nose, Throat: Normocephalic,
atraumatic, PERRLA, Conjunctiva normal, Nares
normal, Oropharynx moist and clear
Neck: Supple with normal range of motion, No
lymphadenopathy, no thyromegaly or palpable
nodules
Cardiovascular: S1S2, regular, rate, and rhythm
without murmurs, gallops, or rubs
Lungs: Clear to auscultation with normal effort
Neurologic: No deficits
Skin: warm and dry
What would you order now?
What tests should I order initially to
screen for hypothyroidism?
What tests should I order initially to
screen for hypothyroidism?
Answer: TSH ONLY
What should I do next if TSH is elevated?
What should I do next if TSH is elevated?
Repeat the TSH along with
a free T4
Total T4 vs. Free T4
• Should I order a Total T4 Level instead of a free T4?—
NO
• 99.97% of T4 is bound to either thyroxine-binding
globulin(TBG), transthyretin(pre-albumin) or albumin
• Total and free T4 levels can be discordant due to
binding protein abnormalities from drugs, illness, and
genetics
• “Direct” free T4 assays don’t actually measure free T4
levels. Instead they provide values that take binding
protein abnormalities into account.
Settings where TSH alone is not useful:
• Known or suspected pituitary or hypothalamic
disease
• Hospitalized patients (sick euthyroid syndrome)
• Patients on medications or with underlying diseases
that can affect TSH secretion
Patient Case
Lab Results:
TSH: 9.80 (0.450-4.500)
T4, total: 6.3 (4.5-12.0ug/dL)
Other Labs to consider adding on
Thyroid Peroxidase: 180 (023IU/ml)
Thyroglobulin Ab: 1.3 (0.0-0.9IU/ml)
Hypothyroidism
• High TSH and low free T4—>Clinical Hypothyroidism
• Treatment can be started immediately if the patient is
symptomatic
• High TSH and normal free T4—>SubClinical Hypothyroidism
• Further evaluation should be considered before starting treatment
• When should I start treatment with this?
• TSH above 10
• Symptoms?
• When the patient is at high risk for progression to overt hypothyroidism
• Hashimoto’s disease-positive thyroid autoantibodies
• Palpable diffuse goiter
• FH of hypothyroidism
• Women who are pregnant, wish to become pregnant or ovulatory dysfunction
Primary Hypothyroidism-Causes
• Hashimoto’s thyroiditis (chronic autoimmune thyroiditis)-Most
common cause in the U.S.
• Iodine deficiency: Most common cause in the world
• Other Causes:
• Iatrogenic (thyroidectomy, radiation)
• Drugs-thionamides, lithium, amiodarone, interferonalfa, interleukin-2, perchlorate
• Transient hypothyroidism
• Congenital thyroid agenesis, dysgenesis, or defects in
hormone synthesis
• Infiltrative diseases-fibrous thyroiditis,
hemochromatosis, sarcoidosis
Hashimoto’s Thyroiditis
• Autoimmune disorder where the immune system
attacks the thyroid leading to hypothyroidism.
• Characterized by gradual thyroid failure, with or
without goiter formation
• Affects 14 million people in the United States alone.
• 7 times more common in women than men.
• Causes: Infection, stress, gender, pregnancy, iodine
intake, radiation exposure.
• Thyroid autoantibodies(anti-thyroid peroxidase
and anti-thyroglobulin autoantibodies) are 95%
positive in patients with this. These antibodies are
directed against TPO and TG, resulting in a
lymphocyte infiltration of the thyroid gland, which
causes it to cease functioning partially or entirely.
Iodine Deficiency
Table 1: Recommendations for iodine intake (µg/day) by
age or population group
a
Recommended Daily Allowance. b Adequate Intake. c Recommended Nutrient Intake.
Age or
population
groupa
U.S.
Age or
Institute population
of
groupc
Medicine
(ref.5)
Infants 0–12
months b
110-130 Children 0-5
years
Children 1-8
years
90>
Children 9-13
years
120>
Adults ≥14 years
World
Health
Organization
(ref.1)
FIG. 1. Large nodular goiter in a 14-yr-old
boy photographed in 2004 in an area of
severe IDD in northern Morocco, with
tracheal and esophageal compression and
hoarseness, likely due to damage to the
recurrent laryngeal nerves
90
Children 612 years
120
150
Adults >12
years
150
<Pregnancy
220
Pregnancy
250
Lactation
290
Lactation
250
Zimmermann, M. B. Endocr Rev 2009;30:376-408
Imaging for Thyroid
• Should I get a Thyroid Ultrasound
for Hypothyroidism?--No
• “Heterogeneic echotexture with 12
left-sided and 16 right-sided
nodules measuring 2-8mm in size”
Hashimoto’s Thyroiditis
• Should I order a Thyroid Uptake
Scan for Hypothyroidism?—No,
your patient will not be happy with
you.
Treatment of Hypothyroidism
•
Levothyroxine(Synthroid) or LT4
•
100% thyroid replacement is roughly 1.6mcg/kg/day(112mcg in a
70kg adult)
•
Euthyroidism is achieved more rapidly when total replacement
dose started, however hyperthyroidism may occur if patient has
mild hypothyroidism prior to initiation of medication.
•
Clinical judgement necessary based on TSH level and clinical
symptoms.
•
Generic vs. Brand?
•
Cytomel: synthetic pure T3, uniform, fast absorption, fast onset.
Greater risk of toxicity, twice daily dosing.
How to take Levothyroxine/Synthroid?
• Only about 50% of LT4 is absorbed under optimal conditions
• It can be reduced with food and medications
• Medications
• calcium carbonate
• ferrous sulfate
• PPIs
• bile acid resins
Synthroid Dosing Guidelines
Some Common Over The Counter Thyroid Supplements
Armour Thyroid
Is Armour Thyroid better than Levothyroxine
because it’s natural?
Not necessarily…
What is it?
• Desiccated porcine thyroid
• 1 grain(60mg) contains 38mcg T4 and 9mcg
T3(equivalent to 36mcg T4).
• T3:T4 ratio is much higher in pigs than in humans(1:20
to 1:100)
• T4 and T3 levels should never be used for monitoring.
• FDA regulated: Can use if patient insists and TSH is
monitored.
• AACE do not recommend using this as first line
treatment
How Often should I monitor TSH Levels?
How Often should I monitor TSH Levels?
Answer: 6-8 weeks
Once stable, every 6 months