Thyroid & Parathyroid Flashcards
Hypoparathyroidism 1* & 2* types
Primary: loss of function is due to glandular issue, so ionized calcium will be low
Secondary: loss of function is in response to hypercalcemia, so calcium levels are likely to be high
There is currently no curative treatment for either type, so electrolyte management is critical
Parathyroid hormone is released in response to drops in extracellular calcium ions, hPTH has what effects?
- Increases osteoclast activity
- Decreases absorption of phosphorus
- Calcium retention in distal tubule
- 1-hydroxylation of vitamin D in the kidney
(Note that this is an example of the many potential problems with 25-OH vitamin D screening)
(Also Note that these effects are not always permanent after thyroid surgery.)
Dietary recommendations for (primary) hypoparathyroid patients
Aim for 1000-1500 mg of calcium per day
Diet should also be rich in magnesium and potassium, as well as low in phosphorus
(This will push toward a plant-based and minimally processed diet)
- Rich in legumes and seeds, in particular
- You’ll want to keep preserved meats and other added phosphate foods under control.
- A DASH-style diet often used in hypertension management would meet these goals well
Patients supplement with extra nutrients, which ones?
Calcium supplementation is a mainstay of treatment, often at 500 mg of elemental calcium q 6 hrs.
Note that binding and removing dietary phosphorus is part of treatment goal here, so i.v. wouldn’t replace well
Vitamin D therapy can be tricky
You’ll want to match (1,25)OH vitamin D with OTC parent compound
Dosing of 1,25 is very tricky, and should start at low end and work up
secondary hypoparathyroidism
This is often a paraneoplastic syndrome where an increase in activated vitamin D (1,25-OH) is seen, in turn driving up calcium levels to a dangerous level
*As many as 30% of cancer patients will develop hypercalcemia at some point during progression
- This can be the presenting complaint of many cancers and other conditions (e.g., sarcoidosis)
- Just restriction of calcium will not turn around the problem – there’s a lot of calcium to draw from the bones
- Make sure in this case to keep an eye on BP and kidney stones risk factors
environmental pollutants in the food chain play a role in hypothyroidism
PCB – banned since 1977 in US, these persistent chemicals are fat soluble and bioaccumulate up the food chain
They structurally resemble thyroid hormone, and possibly lead to secondary hypothyroidism Bisphenol A appears to antagonize thyroid hormone, likely at the receptor level
Brominated fire retardants are widespread in human circulation, and concentrations have increased by almost 10 times over past 35 yrs
Iodine supplements:
Wolff-Chaikoff effect:
Excess iodine supplementation induces a hypothyroid effect, usually transient for about 3-10 days.
*This is the basis for population potassium iodide treatment in case of nuclear accident
Iodine supplements:
Jod-Basedow effect:
Hyperthyroidism triggered by iodine administration
*Happens in patients with goiter, Graves, cancers, not in euthyroid patients
Goitrogens:
Goitrogen is a historical term that refers to a hypothetical quality of specific foods / medications that can impair thyroid function, leading to goiter formation.
(Sheep that grace on Brassica foods)
*Glucosinolates in Brassica foods, broken down in vivo to isothiocyanates, are one category of potential concern, Cooking reduces isothiocyanate by about a third.
Soy isoflavones can interfere with thyroid peroxidase (thus iodination of tyrosine), and potentially with thyroid iodine uptake, as well. It does not appear that moderate doses of soy isoflavones interfere w/ absorption of thyroid medications
Gluten and thyroid disease
There is not evidence I can find that one is directly causing the other, nor that elimination of gluten from the diet can influence the progression of thyroiditis
*And, in fact, there have been reports of restrictive diets causing iodine deficiency
Supplements for hypothyroidism
There are multiple RCT showing selenium leading to suppression of autoantibodies in Hashimoto’s thyroiditis.
Using seaweed as a food supplement is potentially problematic:
- Especially the brown species, which tend to concentrate iodine more than red ones do
- There have been reports of thyroid function improvement upon d/c of dietary seaweed
- Epidemiology has tied seaweed consumption with increased thyroid disease risk, both hypo and hyper
Thyroid disease – supplements for hyperthyroidism
- *Lithium:
- Some CAM doctors have proposed supplemental lithium to keep hyperthyroidism under control
- Lithium does suppress thyroid function at usual 300 mg tid dose
- Works by inhibition of hormone release from gland, so goiter may result
- You’ll also potentially see weight gain, fatigue, immune changes, and increased diabetes risk.
**L-carnitine may antagonize T3/T4 at receptor level in thyroid storm
- *Glucomannan as a thyroid binder may help. Dose 1.3 g bid
- *Cholestyramine has been used, too. Dose is 2 g bid
(Note that both of these trials also used a beta-blocker for addt’l sx management)
Thyroid disease – CAM adjuncts to radioiodine therapy
You’ll ALWAYS recommend a low iodine diet x 2 wks prior to tx
- Our big immediate concern is prevention of loss of salivary function
- Conventional treatment is amifostine, a potent IV antioxidant
- Proposed treatments, based on small trial results, are sugarfree gum with xylitol, lemon candies, and lemon juice (Sample tx: 1-2 candies q 2-3 hrs x 5 days post tx)
If significant damage occurs, you’ll need to protect dental health…
- Xylitol candy/gum (Antimicrobial)
- artificial saliva products (e.g., Biotene)
Cushing’s syndrome and Cushingoid presentations:
- Excessive adrenal hormone can impair insulin response, leading to increased blood sugar.
- Increased urinary calcium loss can lead to bone deterioration
Electrolytes:
Hypokalemia, in particular. Magnesium loss can also occur
management tips in Cushingoid presentations:
- sodium restriction to help manage edema (Leg cramps are often a non-specific clue to electrolyte imbalance)
- High potassium diets are often helpful for blood pressure management
