Endo Exam 2

What releases prolactin?

PRH/TRH

What part of the hypothalamus produces PRH?

paraventricular nucleus

What is prolactin inhbited by?

Dopamine

Where is dopamine secreted from in the hypothalamus?

arcuate nucleus

What type of hormone is prolactin and what mechanism does it use?

Peptide hormone

tyrosine kinase mechanism

What is prolactin’s target?

Mammary glands→ development and milk production

What anterior pituitary cell produces prolactin?

lactotrophs

What does dopamine inhibit?

adenylyl cyclase activity→ reduces cAMP levels

Prolactin is the major hormone responsible for ___

milk productions (lactogenesis)

Prolactin’s milk production secretion is in response to __

suckling

What are the component of milk in mammary glands?

1. Lactose

2. Casein

3. Lipids

At puberty, what is prolactin’s action?

estrogen and progesterone stimulates proliferation and branching of mammary ducts

What is the most common cause of prolactin deficiency?

Sheehan syndrome

T/F Prolactin is involved in milk let down (ejection reflex)

False- oxytocin

Follicular epithelial cells release __

Thyroid hormones

Parafollicular (c cells) release __

Calcitonin

Chief cells of the parathyroid gland release __

parathyroid hormone

What anterior pituitary cell releases thyroid hormones?

Thyrotrophs

What secretes thyroid hormones?

TRH

How is thyroid hormone secreted?

TRH (Phospholipase C)→TSH (Adenylyl Cyclase)→ Thyroid hormones (T3 and T4)(steroid)

What is the role of TSH?

1. secrete thyroid hormones

2. growth of thyroid tissue

What does the thyroid produce more of T3 or T4?

T4 (80%)→ longer half life

T/F T3 is more active than T4

True

What are the 6 steps of thyroid hormone synthesis? (ATE ICE)

1. Active transport of iodide into follicular cell via the sodium-iodide symporter

2. Thyroglobulin→formed into follicular ribososmes and placed into secretory vesicles

3. Exocytosis of Thyroglobulin into follicle lumen→stored as colloid

4. Iodide oxidation and iodination of thyroglobulin (organification)→TPO

5. Coupling/Conjugation

6. Endocytosis of iodinated thyroglobulin back into follicular cell

Who requires the most iodide?

pregnant and lactating women

What is goiter and what causes it?

non-cancerous abnormal enlargement of the thyroid gland

due to iodine excess or deficiency

What is wolff-chaikoff effect?

reduction of thyroid hormones levels caused by ingestion of large amounts of iodine

T/F high iodine can induce hypo or hyperthyroidism

true

Where does T4→T3 conversion take place?

Liver and gut

What enzyme converts T4-T3?

5’ Deiodinases (D1, D2, D3)

What converts portions of T4 into reverese T3?

D3

T/F RT3 is active

False- inactive

Most T4 and T3 circulates bound to ____ (TQ)

Thyroxine-binding globulin (TBG)

What type of hormones are T3 and T4?

amine- steroid like

What effect does thyroid hormones have on BMR?

increase activity of Na+, K+ ATPase= increased oxygen consumption, BMR, and heat production

What effect does thyroid hormones have on metabolism?

increases glucose absorption from GI tract

Thyroid hormones increase both protein synthesis and degradation… overall their effect is ___

catabolic

T/F In the perinatal period, thyroid hromone is essential for normal maturation of the CNS

True

What can hypothyroidism in the perinatal period cause?

intellectual disabilites

Thyroid hormones interact with the ___

sympathetic nervous system

What is the MC cause of hyperthyroidism?

Grave’s disease

What antibodies attack/bind to thyroid cells and in turn increase secretion of thyroid hormones and hypertrophy of the gland?

TSI and TRab

What are some other causes of hyperthyroidism besides grave’s disease?

1. Thyroiditis (may also cause hypo)

2. Taking too much thyroid meds

3. Pituitary tumor

4. Toxic nodular goiter

5. Hyper-functioning thyroid adenoma

6. Jod Basedow Syndrome (too much iodine)

7. Neonatal Hyperthyroidism

What does the TSI index have to indicate for grave’s dx to be positive?

More than 1.8

What is a normal subclinical hyperthyroidism range on TSI index?

1.3-1.8

T/F TSI mimics TSH and binds to receptors→increased production of TH

True

What are some symptoms of hyperthyroidism?

1. weight losee

2. excessive heat production

3. rapid heart rate

4. diarrhea

5. goiter

What are some complications of hyperthyroidism?

1. Heart→ congestive heart failure

2. Brittle bones→ osteoporosis

3. Eye problems→ “bulging eyes”

4. Red swollen skin→ grave’s dx

1/3 cases of graves get ___

Graves’ ophthalmopathy

T/F TED is a thyroid condition

False- TED is an eye condition that can occur in those with graves’ dx

What is a thyroid storm?

rare and life threatening condition that occurs when your thyroid suddenly produces and releases large amounts of thyroid hormone

symptoms are severly exaggerated from hyperthyroidism

A severe state of hypermetabolism is present with what condition?

Thyroid storm

If lab results show high T4 and low TSH, then you have ___

primary hyperthyroidism

If lab results show you have high T4 and high TSH, you have ___

secondary hyperthyroidism

Lab results show high T4, high TSH, and high TRH, you have ___

tertiary hyperthyroidism

What over the counter supplement can alter thyroid testing?

Biotin

can falsely raise T4 and T3 levels

If blood work indicates hyperthyroidism, what test should be ran to see how much collects in the thyroid gland?

radioactive uptake test

What does a high uptake of radioactive iodine mean?

thyroid is producing to much thyroxine= graves dx

What does low uptake of radioactive iodine mean?

T4 stored in the thyroid is leaking in the bloodstream= thyroiditis

What are the three treatment options for hyperthyroidism?

1. Radioactive iodine

2. Anti-thyroid medication

3. Thyroidectomy

What is the #1 cause of hypothyroidism?

Hashimoto’s thyroiditis

What antibodies attack the thyroid gland wiht hashimoto’s thyroiditis?

TgAB/ TPOAb

What are the lab results of someone with hashimoto’s?

low T4, high TSH

high TSH causes goiter

When someone has hypothyroid symptoms… but labs are normal, what’s another area to consider?

ADRENALS

weak adrenals→hypothyroid symptoms

Adrenal stress→ interferes with conversion of T4 to T3

T/F Elevated levels of cortisol in circulation can slow thyroid hormone production

trueT

T/F prolonged elevated levels of cortisol can cause excess estrogen to accumulate leading to increased TBS= decrease T4

true

What are some symptoms of hypothyroidism?

1. weight gain

2. decreased metabolic rate

3. decreased heart rate

4. decreased heat production

5. goiter

What happens in severe hypothyroidism?

myxedema coma

What causes myxedema coma?

hypothyroidism + stressor that triggers an increase in metabolism→depletes Th= crisis

What is it called if hypothyroidism in perinatal period is untreated and results in irreversible form of growth and intellectual disabilities?

Cretinism

What test occurs at 5 days old 9 rare but serious health conditions?

Heel prick test

If lab shows T4 low, TSH high, you have __

primary hypothyroidism

If lab shows you have low T4 and low TSH, you have ___

secondary hypothyroidism

If lab shows you have low T4, low TSH, and low TRH, you have ___

tertiary hypothyroidsm

What is the treatment for hypothyroidism?

thyroid hormone replacement therapy→ levothyroxine

Poor gut health can ___ thyroid function

suppress

What does poor gut health trigger?

hashimoto’s and decreased thyroid function= inflammation

leaky gut

SCFA + thyroid horomones can ___

strengthen tight junctions and prevent leaky gut

What two probiotics are most associated with thyroid and are often reduced?

Lactobacillaceae and Bifidobacteriaceae

What minerals are important to the thyroid? (TQ)

1. iodine

2. selenium

3. zinc

4. iron

What food sources are high in iodine?

1. seafood and seaweed

2. Dairy products

3. iodized salt

What food sources are rich in selenium?

1. brazil nuts

2. seafood

3. organ meats

What mineral is required for 5’ deiodinase to convert T4→T3?

Zinc

What food sources are high in zinc?

1. oysters

2. red meats

3. pork

4. chicken

Iron is essential and supports what thyroid function?

efficient iodine utilization and thyroid hormone synthesis

T/F iron is needed to convert T4→T3

True

What food sources are rich in iron?

1. lean meat

2. seafood

3. poultery

When pregnant high levels of estrogen inhibit breakdown of TBG causing increase in TBG levels and in turn leads to ___ levels of T4

decreased

What is hyperemesis gravidarum?

severe nausea and vomiting leading to weight loss and dehydration during pregnancy

What is believed to cuases hyperemesis gravidarum?

high levels of hCG

thyroid nodules produce too much TH

What are the treatments of hyperthyroidism during pregnancy?

Mild- no tx

Antithyroid meds if severe

What are possible fetal complications with mom having hypothyroidism? (2)

1. low IQ

2. problems with normal development

What are the treatment options of hypothyroidism?

hormone replacing medications

What is postpartum thyroiditis?

inflammation of the thyroid that occurs during the first year after giving birth. Inflammation causes the thyroid to lead TH, causing hyperthyroidism→ shifts to hypothyroidism

T/F postpartum thyroiditis is an inherited condition

false-autoimmune

T/F thyroid cancer is 3x more likely in men

false-women

What are the first two things used to test if a thyroid nodule is benign or cancerous?

1. Ultrasound

2. Fine needle aspiration cytology

What would a hot vs cold nodule indicate?

Hot→cyst filled (benign)

Cold→solid nodule (more likely cancerous)

What are the three types of differentiated thyroid cancers? (TQ)

1. Papillary thyroid cancer (MC)

2. Follicular thryoid cancer

3. Other thyroid cancer

What is the type of undifferentiated thyroid cancer on the follicular epithelial cell side?

Anaplastic thyroid cancer