pasireotide
Meaning of pasireotide: Built to reach a receptor its predecessor barely touches, at the cost of pushing blood sugar up in a large share of users.
Definition of pasireotide
Pasireotide is a laboratory-made copy of somatostatin, the hormone that works as a general off switch for other hormones. It attaches to four of the five somatostatin receptor types found on hormone-producing cells and quiets their output. Given by injection, it is used for two conditions of hormone excess caused by pituitary tumors when surgery has not brought them under control.
What does somatostatin do?
It is a short protein made in the brain, the gut and the pancreas whose whole role is to turn things down. It damps the release of growth hormone from the pituitary, of insulin and glucagon from the pancreas, and of several hormones that drive digestion. Natural somatostatin survives only minutes in the bloodstream, which makes it useless as a medicine, so copies were built that resist breakdown and last for hours or, in a depot form, for weeks. Cells respond to it through five different receptor subtypes, and which subtypes a copy prefers decides what it is good for.
How does it differ from the older analog?
| Feature | Octreotide | Pasireotide |
|---|---|---|
| Receptor preference | Chiefly subtype 2 | Subtypes 1, 2, 3 and 5, strongest at 5 |
| Main targets | Acromegaly, hormone-secreting gut tumors | Cushing disease, acromegaly still uncontrolled |
| Effect on blood sugar | Modest | Marked rise, common enough to expect |
Why does it raise blood sugar?
The receptor it engages most strongly is also the one governing insulin release, and it suppresses the gut hormones that would normally prompt the pancreas to release insulin after a meal. Blood sugar therefore climbs soon after treatment begins, diabetes that was previously hidden can surface, and existing diabetes tends to worsen. Glucose is followed closely for that reason. Other effects follow from switching off the same signals elsewhere: bile empties from the gallbladder more sluggishly, so gallstones and sludge form, and loose stools, nausea and a slowed pulse are common. Because the tumors carry these receptors on their surface, the same biology allows them to be located on a scan by somatostatin receptor scintigraphy.
Used in a sentence
Pasireotide was started after surgery failed to normalize cortisol production.
Good to know
Its reach across somatostatin receptor subtypes is what separates it from octreotide, and the same breadth accounts for a rise in blood sugar frequent enough that glucose is monitored from the outset.