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EMiNEM Case #2: Answers and Discussion

Summary

This case is a good example of how imaging for parathyroid tissue prior to surgery may have been beneficial. A repeat MIBI scan showed a right inferior PTH adenoma that had not been removed at the original surgery. Looking at the surgery pathology specimens, one adenoma was removed with surgery along with three other parathyroid glands, one of which was incomplete. This was the right inferior adenoma that was not removed at the initial surgery. If Cinacalcet would have been available to this patient, this may have also been a preferred treatment due to its ability to decrease PTH levels as well as both phosphate and calcium to some degree.

Question #1

What therapies for the bone mineral metabolism parameters would you institute after the first clinic visit with the blood work?

Dietary phosphate review and restriction only

This would be important to do here as the calcium is the upper limit of normal, and the PTH is already elevated. Although, more than just a dietary review and PO4 restriction would be important at this stage.

Dietary phosphate, review and restriction along with calcium based phosphate binder

The phosphate is not above target and therefore a binder is not indicated. Use of a calcium base phosphate binder with in the calcium upper limit of normal, may lead to further increase calcium, unless there is something identified on the diet history to suggest there is a higher than normal intake.
Dietary phosphate, review and restriction along with non-calcium based phosphate binder
At this time, the phosphate is within an acceptable range, and therefore, this is not necessarily needed at this time.

Dietary review with phosphate restriction, and active vitamin D sterol
One may be concerned about further increase calcium.

Dietary review with phosphate restriction and use of nutritional vitamin D.
This may be the safest to institute at this time. At this level of kidney function there may still be conversion to active 1,25 vit D. 

Linking the comments back to the mineral metabolism grid, at the present time, the PTH is elevated, but not outside the recommended target range of 10-50 pmol/L. It may be prudent to monitor PTH levels, however the high-normal calcium is worrisome since no therapy has been instituted. The best option may be to assess diet for both phosphate and calcium intake and modify both as needed and to start with nutritional vitamin D to see if it has any impact on maintaining or decreasing the PTH level. If the PTH level continues to rise despite nutritional vit D then a switch to active vit D may be needed.

Question #2

At this time, your treatment strategy would be which of the following?

Discontinue the Tums and start a non-calcium based phosphate binder but keep the vitamin D active sterol in place.
It may be possible to try this scenario, although one should be prepared to discontinue the active vitamin D sterol within another 2 weeks to a month if the calcium remains high.

Stop the Tums and switch to a non-calcium based phosphate binder and discontinue the active vitamin D sterol.
This could be done, however, there is concern that even with a high calcium, the PTH has continued to rise.

Stop the active vitamin D sterol and add a non-calcium based phosphate binder on to the Tums.
Not the preferred approach as the vitamin D sterol is a fairly low dose.

Discontinue the vitamin D and start Cinacalcet but keep the Tums in anticipation of a lower serum calcium.
If available, Cinacalcet may be quiet useful in helping to control the PTH level. The Tums should be stopped, but could be added back if the serum calcium dose decrease and the patient becomes symptomatic.

Stop the vitamin D sterol, start Cinacalcet and switch to a non-calcium based phosphate binder.

This would be the preferred approach if there is the ability to obtain Cinacalcet for this patient. A calcium based binder could be added back in if the serum calcium falls and the patient is symptomatic. 

Question #3

Your management at this time would be which of the following?

Discontinue the vitamin D sterol and institute Cinacalcet and increase the non-calcium phosphate binder. 

If Cinacalcet is available for this patient, this may be the preferred approach. It would also be the preferred approach if the patient is considered to be a high risk surgical patient.

Discontinue the vitamin D sterol and increase the non-calcium based phosphate binder and refer for parathyroidectomy.
If there is no ability to use Cinacalcet, then this would be the approach, but this will likely not control the PTH level. However, one should wait until there are some symptoms of hyperparathyroidism, such as bone pain.

Discontinue the vitamin D sterol
Although this would be important to do, it is not going to help with the patient’s management if done in isolation.

Do imaging of the parathyroid glands and refer for surgical opinion
Imaging the parathyroid glands may be important to determine if there is identification of a specific adenoma. This imaging may or may not be required prior to surgery, however it is not the only thing that needs to be done at this point in time as the calcium is still elevated as is the phosphorus. 

Question #4

Based on the laboratory investigations, your approach to management at this time would be which of the following

Try and seek compassionate Cinacalcet for use to control the PTH.
Use of Cinacalcet may be a good option at this time as the patient has failed surgery.

Add additional non-calcium based phosphate binders for control of phosphate.
Although non-calcium based phosphate binders may be needed, some of the phosphate may be coming from bone as a result of the elevated PTH level.

Do a MIBI scan looking for residual PTH tissue or a nodule.
At this point, this may be the preferred option prior to referring back to the surgeon. It is possible that an adenoma was missed at the time of surgery.

Refer back to surgery for repeat surgery for parathyroidectomy and thymus removal
This would be the next step after the MIBI scan. If no adenoma was found, either within the thyroid gland or extra thyroid focus of activity, then repeat surgery with thymectomy may be preferred as it has been shown in studies that parathyroid cells within the thymus gland may be the cause of relapse of hyperparathyroidism.