Thyroid Flashcards
What is the thyroid pathway?
_____ cells secrete thyroid hormone
_____ cells secrete Calcitonin
Follicular Cells -> Thyroid Hormone
Parafollicular Cells (C-Cells) -> Calcitonin
How does calcitonin control Ca+ and K+ levels?
INHIBITING OSTEOCLAST ACTIVITY -> stops bone breakdown and decreases the amount of Ca+ in the blood (pee out less Ca+)
Does Calcitonin want Ca+ in the blood or bones? Is it secreted by the thyroid when serum Ca+ is high or low?
bones
Secreted when high serum Ca+
Deposition or Resorption?
Osteoblasts -> bone _____
Osteoclasts -> bone _____
Osteoblasts -> Bone Deposition
Osteoclasts -> Bone Resorption
Deposition: “Deposit into the bone”
Resorption: “Reabsorb into bloodstream”
Does T3 or T4 control metabolic rate?
Which is biologically active?
T3
T4: Thyroxine (Tetraiodothyronine)
T3: Triiodothyronine
Which lasts longer, T3 or T4?
T3 (24hrs)
T4 (7-10 days) Reservoir
Most common causes of hypothyroidism?
T4/T3 deficiency
Worldwide -> Iron deficiency
US -> Autoimmune thyroid disease (Hashimoto Disease)
Congenital hypothyroidism
Cretinism -> severe neonatal iron deficiency due to maternal iron deficiency
Who needs thyroid screening? how often?
35yo (q 5 years)
Pregnant - once in 1st Tri
Women > 60yo
Type I DM or other autoimmune Dz
Hx neck irradiation
Cretinism
severe neonatal iron deficiency due to maternal iron deficiency
Hypoparathyroidism: Primary vs Secondary vs Tertiary
- Primary -> thyroid gland itself cannot produce enough T3/T4
- Secondary -> Abnorm pituitary secretes LOW TSH
- Tertiary -> Hypothalamus does not secrete enough TRH
Primary vs Secondary hypothyroid Trmnt
Both: Levothyroxine (synthetic T4)
Primary: monitor TSH
Secondary: Monitor T4
Liothyronine:
Synthetic T3 or T4?
Used for sole maintenance? Preferred when?
T3
NOT used for sole maintenance (can be used in combo with T4 (Levothyroxine) in small doses)
Preferred when GI absorption is impaired
Is Hashimotos hypo- or hyper- thyroid?
Autoimmune Hypothyroidism
MCC of Hypothyroidism in the US (for those >6yo)
Hashimotos
TSH and T4 labs for Hoshimotos Hypothyroidism
Low TSH & Low T4
Hashimotos is autoimmune hypothyroidism (thyroid autoantibodies)
3 MC forms of Hyperthyroidism
- Graves Disease (Diffuse Toxic Goiter)
- Plummer Disease (Toxic Nodular Goiter)
- Toxic Adenoma
What causes Grave’s Disease?
Thyroid-stimulating immunoglobulins (TSIs) bind and activate thyroid-stimulating hormone (TSH) -> thyroid gland grows & follicles secrete EXCESS thyroid hormone
Which hyperthyroid disease is this?
SS: diffusely big and smooth thyroid gland, wt loss, warm skin, fine hair, bulging eyes, tachypnea, tachycardia, hyperactive bowel sounds, hyperactive DTRs, restlessness, anxiety, irritability, insomnia
WU: Low TSH, diffuse radioactive iodine uptake
Grave’s Disease
Grave’s Disease Trmnt
Radioactive iodine
OR
Antithyroid Meds - Methimazole or PTU (Propylthiouracil)
Use Radioactive iodine over Antithyroid meds if:
- large thyroid gland
- Multi SS of Thyrotoxicosis
- High levels of thyroxine
- High titers of TSI
Which Antithyroid med is safe for pregnancy?
Methimazole or PTU (Propylthiouracil)
PTU (Propylthiouracil)
Doesn’t cross placenta
Pregnancy Goal: Thyroid Fn norm or HIGH (never low)
Which hyperthyroid disease is 2nd MC in US & #1 MCC if elderly or endemic country?
Toxic Nodular Goiter (Plummer Disease)
single or multi areas of hyperfunction in the thyroid
Hyperthyroid SS in eldery
- Anorexia
- Wt loss
- Constipation
- Palpitations -> Afib
- CHF SS
- +/- Angina
- +/- hoarse voice
How can goiter result in hoarseness or voice change? Which nerve is affected?
Compression of Laryngeal nerve
