Endocrine Study Guide
HYPOTHYROIDISM
Primary thyroid dysfunction occurs at the gland
Secondary thyroid dysfunction occurs at the pituitary
Tertiary thyroid dysfunction occurs at the hypothalamus
What is hypothyroidism (Hashimoto’s thyroiditis)?
Clinical state that results from either a reduction in the amount of circulating free thyroid hormone, or from
resistance to the action of thyroid hormone.
What is hyperthyroidism (thyrotoxicosis, grave’s disease)
Clinical state that results when the body’s tissues are exposed to an increased level of circulating thyroid
hormone. Manifestations are related to excessive metabolic activities in body tissues.
What is congenital hypothyroidism?
is inadequate thyroid hormone production in newborn infants. It can occur because of an anatomic defect in
the gland, an inborn error of thyroid metabolism, or iodine deficiency in mother
Signs and symptoms
o Abnormal Newborn Screen
o Patent Posterior Fontanel- or generous AF
o Umbilical Hernia
o Jaundice does not clear
o Hypotonia
o Hoarse Cry
o Constipation
o Feeding Difficulties
o Skin Mottling
How is it treated?
Newborn screen will say T4 very low TSH very high.
Get serum levels Free T4 and TSH.
Call us but will start treatment asap 10-15 mcg/kg/day of levothyroxine.
Ongoing management with endo. We follow monthly for first 6 months. Then every other month.
o What happens if it is not treated?
Mental retardation
Growth and developmental delays
Early treatment can save IQ points (research shows).
Should treat within first week if possible
ensure normal growth and neuropsychological development
What lab values would you expect to see with:
Primary hypothyroidism
o TSH elevated; T4 low; T3 normal
, subclinical hypothyroidism
o TSH elevated; T4 normal; T3 normal
Primary hyperthyroidism
o TSH decreased; T4 elevated; T3 normal
What are the most common forms of
Hyperthyroidism – Grave’s disease -Autoimmune process in which antibodies stimulate the TSH receptor
leading to overproduction of thyroid hormones
Hypothyroidism – Hashimoto’s thyroiditis
What test would be done in a patient with secondary hypothyroidism to determine whether the cause is
hypothalamic or pituitary related? (hint refer to PEARLS)
o If a patient has secondary hypothyroidism you need to determine whether cause is hypothalamic or pituitary
problem.
o A thyroid-releasing hormone (TRH) test can determine this.
o When TRH is injected IV a normally functioning pituitary will result in an increase of TSH that can be
measured in about 30 minutes.
o No increase in TSH after injected of TRH suggest a malfunctioning pituitary gland.
How do you determine dosage of Levothyroxine?
o Usual doing 1.7 mcg/kg for adults and 1.0 mcg/kg for elderly (This is based on ideal body weight and not
actual in an obese patient):
o START LOW GO SLOW. NEVER HURTS TO START A LITTLE LOWER THAN THIS DEPENDING ON
SYMPTOMS
o Doses are 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg and
200 mcg
o Anyone 50-60 start on 50 mcg
o Elderly 65 and over: 25 mcg
o Increase every 3-6 weeks as needed by 12-25mcg until normal TSH
o Small decreases may be needed as patient ages
o Upper limit of normal in TSH in 80-year-old is 7.5
o TOO MUCH THYROID CAN CAUSE ATRIAL FIBRILLATION (MAY BE A QUESTION ON BOARDS)
How does Levothyroxine differ from Armour thyroid?
o Armour Thyroid
o Derived from bovine animal thyroids
o Contain thyroxine and triiodothyronine
o Have variable biologic activity
How often does a patient need to be recheck when titrating dose?
o Reevaluation with a serum TSH need not be performed at intervals less than 6 weeks
What are risks of too much Levothyroxine?
, common A fib,
accelerated bone loss
How would you manage a patient with hyperthyroidism? (See PEARLS) American Family Physician
article is excellent
Always refer out for hyperthyroidism. May given low beta blocker to slow heart rate until you can get them
into Endocrinologist. If A-fib or very symptomatic (thyroid storm crisis) send to ER
Surgery – thyroidectomy
See management of Grave’s disease
Know that TSH is the lab test done to determine whether or not thyroid medication needs to be raised or lowered,
not T4.
Know that with subclinical hypothyroidism, treatment is controversial. I would make the decision based on
whether or not patient is symptomatic and TSH 10 or greater
What is Grave’s disease?
Autoimmune disorder causing hyperthyroidism
Presents with
o General - Increased basal metabolic rate, weight loss despite increase or similar appetite
o Skin - Warm, most, fine skin; increased sweating; fine hair; vitiligo; alopecia; pretibial myxedema
o Head, eyes, ears, nose, and throat - Chemosis, conjunctival irritation, widening of the palpebral fissures,
lid lag, lid retraction, proptosis, impairment of extraocular motion, visual loss in severe optic nerve
involvement, periorbital edema
o Neck - Upon careful examination, the thyroid gland generally is diffusely enlarged and smooth; a well-
delineated pyramidal lobe may be appreciated upon careful palpation; thyroid bruits and, rarely, thrills
may be appreciated; thyroid nodules may be palpable.
o Chest - Gynecomastia, tachypnea, tachycardia, murmur, hyperdynamic precordium, S3, S4 heart sounds,
ectopic beats, irregular heart rate and rhythm
o Abdomen - Hyperactive bowel sound
o Extremities - Edema, acropachy, onycholysis
o Neurologic - Hand tremor (fine and usually bilateral), hyperactive deep tendon reflexes
o Musculoskeletal - Kyphosis, lordosis, loss of height, proximal muscle weakness, hypokalemic periodic
paralysis in persons of susceptible ethnic groups
o Psychiatric - Restlessness, anxiety, irritability, insomnia, depression
How is it managed?
Radioactive iodine treatment
Antithyroid drug therapy
Thyroidectomy
Ophthalmologist for ophthalmopathy
Meds for symptom management i.e. beta-blockers
THYROID STORM is an emergency
High rate of relapse after medications stopped
HYPOTHYROIDISM
Primary thyroid dysfunction occurs at the gland
Secondary thyroid dysfunction occurs at the pituitary
Tertiary thyroid dysfunction occurs at the hypothalamus
What is hypothyroidism (Hashimoto’s thyroiditis)?
Clinical state that results from either a reduction in the amount of circulating free thyroid hormone, or from
resistance to the action of thyroid hormone.
What is hyperthyroidism (thyrotoxicosis, grave’s disease)
Clinical state that results when the body’s tissues are exposed to an increased level of circulating thyroid
hormone. Manifestations are related to excessive metabolic activities in body tissues.
What is congenital hypothyroidism?
is inadequate thyroid hormone production in newborn infants. It can occur because of an anatomic defect in
the gland, an inborn error of thyroid metabolism, or iodine deficiency in mother
Signs and symptoms
o Abnormal Newborn Screen
o Patent Posterior Fontanel- or generous AF
o Umbilical Hernia
o Jaundice does not clear
o Hypotonia
o Hoarse Cry
o Constipation
o Feeding Difficulties
o Skin Mottling
How is it treated?
Newborn screen will say T4 very low TSH very high.
Get serum levels Free T4 and TSH.
Call us but will start treatment asap 10-15 mcg/kg/day of levothyroxine.
Ongoing management with endo. We follow monthly for first 6 months. Then every other month.
o What happens if it is not treated?
Mental retardation
Growth and developmental delays
Early treatment can save IQ points (research shows).
Should treat within first week if possible
ensure normal growth and neuropsychological development
What lab values would you expect to see with:
Primary hypothyroidism
o TSH elevated; T4 low; T3 normal
, subclinical hypothyroidism
o TSH elevated; T4 normal; T3 normal
Primary hyperthyroidism
o TSH decreased; T4 elevated; T3 normal
What are the most common forms of
Hyperthyroidism – Grave’s disease -Autoimmune process in which antibodies stimulate the TSH receptor
leading to overproduction of thyroid hormones
Hypothyroidism – Hashimoto’s thyroiditis
What test would be done in a patient with secondary hypothyroidism to determine whether the cause is
hypothalamic or pituitary related? (hint refer to PEARLS)
o If a patient has secondary hypothyroidism you need to determine whether cause is hypothalamic or pituitary
problem.
o A thyroid-releasing hormone (TRH) test can determine this.
o When TRH is injected IV a normally functioning pituitary will result in an increase of TSH that can be
measured in about 30 minutes.
o No increase in TSH after injected of TRH suggest a malfunctioning pituitary gland.
How do you determine dosage of Levothyroxine?
o Usual doing 1.7 mcg/kg for adults and 1.0 mcg/kg for elderly (This is based on ideal body weight and not
actual in an obese patient):
o START LOW GO SLOW. NEVER HURTS TO START A LITTLE LOWER THAN THIS DEPENDING ON
SYMPTOMS
o Doses are 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg and
200 mcg
o Anyone 50-60 start on 50 mcg
o Elderly 65 and over: 25 mcg
o Increase every 3-6 weeks as needed by 12-25mcg until normal TSH
o Small decreases may be needed as patient ages
o Upper limit of normal in TSH in 80-year-old is 7.5
o TOO MUCH THYROID CAN CAUSE ATRIAL FIBRILLATION (MAY BE A QUESTION ON BOARDS)
How does Levothyroxine differ from Armour thyroid?
o Armour Thyroid
o Derived from bovine animal thyroids
o Contain thyroxine and triiodothyronine
o Have variable biologic activity
How often does a patient need to be recheck when titrating dose?
o Reevaluation with a serum TSH need not be performed at intervals less than 6 weeks
What are risks of too much Levothyroxine?
, common A fib,
accelerated bone loss
How would you manage a patient with hyperthyroidism? (See PEARLS) American Family Physician
article is excellent
Always refer out for hyperthyroidism. May given low beta blocker to slow heart rate until you can get them
into Endocrinologist. If A-fib or very symptomatic (thyroid storm crisis) send to ER
Surgery – thyroidectomy
See management of Grave’s disease
Know that TSH is the lab test done to determine whether or not thyroid medication needs to be raised or lowered,
not T4.
Know that with subclinical hypothyroidism, treatment is controversial. I would make the decision based on
whether or not patient is symptomatic and TSH 10 or greater
What is Grave’s disease?
Autoimmune disorder causing hyperthyroidism
Presents with
o General - Increased basal metabolic rate, weight loss despite increase or similar appetite
o Skin - Warm, most, fine skin; increased sweating; fine hair; vitiligo; alopecia; pretibial myxedema
o Head, eyes, ears, nose, and throat - Chemosis, conjunctival irritation, widening of the palpebral fissures,
lid lag, lid retraction, proptosis, impairment of extraocular motion, visual loss in severe optic nerve
involvement, periorbital edema
o Neck - Upon careful examination, the thyroid gland generally is diffusely enlarged and smooth; a well-
delineated pyramidal lobe may be appreciated upon careful palpation; thyroid bruits and, rarely, thrills
may be appreciated; thyroid nodules may be palpable.
o Chest - Gynecomastia, tachypnea, tachycardia, murmur, hyperdynamic precordium, S3, S4 heart sounds,
ectopic beats, irregular heart rate and rhythm
o Abdomen - Hyperactive bowel sound
o Extremities - Edema, acropachy, onycholysis
o Neurologic - Hand tremor (fine and usually bilateral), hyperactive deep tendon reflexes
o Musculoskeletal - Kyphosis, lordosis, loss of height, proximal muscle weakness, hypokalemic periodic
paralysis in persons of susceptible ethnic groups
o Psychiatric - Restlessness, anxiety, irritability, insomnia, depression
How is it managed?
Radioactive iodine treatment
Antithyroid drug therapy
Thyroidectomy
Ophthalmologist for ophthalmopathy
Meds for symptom management i.e. beta-blockers
THYROID STORM is an emergency
High rate of relapse after medications stopped
