Calcium Homeostasis in Acromegaly: Effect of Surgical/Medical Treatment and Comparison With Nonfunctioning Pituitary Tumors.
Calcitriol is the active form of vitamin D. Parathyroid hormone (PTH) is secreted by the
parathyroid glands in the neck. Both these chemicals are responsible for keeping the levels
of calcium and phosphorous normal and also play a role in bone health. They can be measured
in the blood. In some disorders, PTH or calcitriol levels are elevated, which results in
increased calcium absorption from the gut, increased calcium in the bloodstream, and
increased calcium excretion in the urine. Increased calcium in the urine can lead to the
development of kidney stones. Increased calcium in the bloodstream can have adverse effects
on the heart, gut, kidneys, and bones.
Acromegaly is a condition where a pituitary tumor secretes excessive amounts of growth
hormone. Patients with acromegaly have been found to have a higher prevalence of kidney
stones, urinary calcium, and serum calcium when compared to normal adults. The reason for
this is unknown but a suggested mechanism is that growth hormone stimulates the production
of calcitriol or PTH. If this is true, then treatment of acromegaly resulting in lower
growth hormone levels should also result in lower blood and urine calcium levels. The
investigators want to see if patients with acromegaly have high calcitriol, and vitamin D
binding protein, or PTH levels and see if they change after treatment of the condition. The
investigators also want to assess the amount of calcium in the urine, before and after
Patients with acromegaly may have disorders of bone health. The reason for this is unknown
but a suggested mechanism is that growth hormone affects bone remodeling. The investigators
want to see if patients with acromegaly have abnormal bone markers, specifically PINP, CTX,
and TRAP, and to see if they change after treatment of the condition.
In order to see if the results are specific to patients with acromegaly, the investigators
also want to check these levels in patients who do not have acromegaly, but have a
"nonfunctioning" pituitary tumor. A nonfunctioning pituitary tumor is one that does not
secrete excessive hormones in the bloodstream.
The specific aims of this study are:
1. To describe baseline calcitriol/PTH status in patients with uncontrolled acromegaly.
2. To assess the change in calcitriol/PTH levels after treatment with acromegaly (surgical
3. To evaluate the calcium and calcitriol/PTH levels in patients with acromegaly compared
to patients with nonfunctioning pituitary adenomas.
This is a voluntary study. Adult patients with a diagnosis of acromegaly or a clinically
nonfunctioning pituitary tumor receiving treatment at the Emory University Pituitary center
will be given the opportunity to enroll in the study. Those that agree to participate will
need to give written informed consent. Approximately 3 tablespoons (44ml) of blood will be
drawn at enrollment for testing of vitamin D status and parathyroid hormone. If patients are
already undergoing a blood draw for standard laboratory tests, then the volume of 44ml of
blood will be obtained at the same time in order to avoid an additional needle stick. In
addition, a 24-hour urine collection will be obtained to assess the amount of calcium
present in the urine. Please note that medical or surgical therapy for your pituitary
condition is determined by your endocrinologist and/or neurosurgeon and not part of the
Within 6 months after treatment for pituitary treatment is initiated, when patients return
to Emory University pituitary clinic for routine visit, laboratory data (vitamin D and
parathyroid hormone) and repeat urine studies (24 hour urine collection) will be collected.
The confidentiality will be respected in all encounters. No personal identifiers are
disclosed in any publications. Hard copy data will be kept securely in a locked office
building with limited access and electronic data will always be password protected with
access available to study personnel only. If abnormal results are discovered as part of
testing done for this study, those results will be released to the patient's primary
physician. All patients will be undergoing standard therapy for their pituitary disorder.
Results of this study may have important implications for future studies that are designed
to evaluate the mechanism of how growth hormone may increase calcitriol levels.
Observational Model: Case Control, Time Perspective: Prospective
To describe baseline calcitriol/PTH status in patients with uncontrolled acromegaly, with subanalyses based on presence of hyperprolactinemia. To assess the change in calcitriol/PTH levels after treatment with acromegaly, with subanalyses based on type of therapy (surgical or medical). To evaluate the calcium and calcitriol/PTH levels in patients with acromegaly compared to patients with nonfunctioning pituitary adenomas, with subanalyses based on presence of hyperprolactinemia in either group.
Baseline and 3-6 months after trreatment of pituitary condition
Adriana Ioachimescu, MD, PhD
United States: Institutional Review Board
|Emory Clinic||Atlanta, Georgia 30365|
|Emory University Hospital||Atlanta, Georgia 30322|