What happens to endogenous PTH during teriparatide therapy?

I've often wondered this. Fortunately, there's a study:

Endocrine Journal Vol. 55 (2008) , No. 3 613-616



36 post-menopausal women with established osteoporosis received teriparatide 20 mcg daily for 18 months and then were followed for another 6 months. You can see that iPTH significantly declines for months 6-18. There was actually no significant increase in calcium.

The authors mention this as a potential way to monitor compliance. I have wondered if teriparatide could be used to treat osteoporosis in patients with mild asymptomatic primary hyperparathyroidism or even secondary hyperparathyroidism. I had assumed that the PTH would be additive and risk driving calcium higher. In fact it may possibly lower PTH in these conditions. That would be an interesting study...

Hypercalcemia

50 yo male w/ Child C cirrhosis, bedbound > 1mos, Ca on admission 11.1, now w/ acute rise to 14.6 and AMS. PTH 15.

Causes:

PTH-dependent: Primary hyperparathyroidism due to parathyroid adenoma or hyperplasia.

PTH-independent: malignancy (MM, Breast Ca., Lung Ca.) Granulomatous Dz (Sarcoidosis, TB), thyrotoxicosis, AI, pheochromocytoma,  medications(esp. thiazides and lithium), Vit D intoxication, milk-alkali syndrome,FHH, immobilization, advanced liver dz, post-renal transplant, HIV/AIDS

Treatment:

Hydration

Bisphosphonates (inhibit osteoclast activity)

Cinacalcet(binds to calcium-sensing receptor on Chief Cells in parathyroid gland and increases sensitivity to extracellular calcium)

Conclusion:

Pt. w/ PTH dependent hypercalcemia +/- PTH-independent causes such as advanced liver dz., immobilization.

Further w/u P

Hydration started, consider treatment w/ bisphosphonates/cinacalcet in future.

Hypercalcemia

50 year old female with liver cirrhosis with altered mental status.
The patient's calcium is 14 and has an elevated ionized calcium.
The patient's PTH is 15.
What are the causes and how do you treat this patients?