Page 78 - Clinical Small Animal Internal Medicine

46 Section 2 Endocrine Disease

has not been reported in cats but in humans, response on MRI. The diabetes resolved two weeks postoperatively
VetBooks.ir rates have been reported to be as high as 90%. However, it and remained in remission for eight months at which time
the patient was euthanized as a result of feline infectious
has been noted that the medication has no effect on
tumor size and thus would be of no benefit in patients
In more recent studies, hypophysectomy has been
with neurologic signs. A single case study using a dopa­ peritonitis.
mine agonist (L‐deprenyl) for the treatment of feline acro­ offered to owners who presented diabetic cats with con­
megaly showed no effect on reducing insulin requirements firmed acromegaly (IGF‐1 >1000 ng/mL, pituitary mass)
or clinical signs of disease. In humans, dopamine agonists to the Royal Veterinary College since 2012. All cats were
are typically only 10–20% effective, but are often used in operated on by one neurosurgeon. Hypophysectomy was
combination with other medications. performed by manual extirpation using fine surgical tools
Increasing the dosage of insulin to improve glycemic via a transoral transsphenoidal approach. Cats received
control and clinical signs of diabetes is the most con­ intensive peri‐ and postoperative monitoring of electro­
servative choice for treating insulin‐resistant diabetic lytes, glucose and blood pressure, and were initially
acromegalics. However, there have been reports that administered conjunctival desmopressin (DDAVP), intra­
some patients suddenly and inexplicably become sensi­ venous infusions of insulin and hydrocortisone, before
tized to insulin, resulting in hypoglycemic crises. In one being transitioned to conjunctival DDAVP, oral hydrocor­
study, several acromegalic cats were euthanized after tisone and levothyroxine and subcutaneous glargine insu­
experiencing hypoglycemic coma. lin. In total, 21 diabetic cats underwent hypophysectomy
from April 2012 to October 2014 (median, range; age: 10.3
years, 5.4–14.8; pituitary height: 6.0 mm, 4.0–10.6; IGF‐1:
Surgical Treatment
1833 ng/mL, 1138 to >2000; fructosamine: 574 μmol/L,
Surgical removal of the pituitary tumor (adenectomy) is the 339–1076). Other than mild pelvic limb weakness, no cat
treatment of choice for acromegaly in human medicine. displayed overt neurologic deficits prior to surgery. Three
The procedure can be performed in cats and dogs, usually (14%) cats died postoperatively. Two cats did not recover
employing complete removal of the entire pituitary from anesthesia and were euthanized within 24 hours;
(hypophysectomy). one cat developed septic meningitis and was euthanized
In veterinary medicine, a transsphenoidal approach is 17 days postoperatively. All surviving cats (n = 18) had a
used involving only a small incision through the soft palate reduction of serum IGF‐1 and 16 cats (89%) showed IGF‐1
and then approaching the pituitary gland through the normalization (median postoperative serum IGF‐1: 38 ng/
basisphenoid bone. Complications associated with the mL (15–1955), P < 0.001). Fourteen of the 18 surviving
surgery include hemorrhage and incision dehiscence. Post cats (78%) achieved diabetic remission; the remaining
surgery, patients are treated with cortisone, L‐thyroxine, four achieved superior glycemic control with lower insu­
and desmopressin. The same surgical procedure is also lin dosages (median fructosamine pre‐ and postopera­
used to treat pituitary‐dependent hyperadrenocorticism tively: 692 and 547μmol/L respectively; median insulin
in both dogs and cats. A study in which seven cats with dose pre‐ and postoperatively: 20.5 and 3.5 units/kg/day
pituitary‐dependent hyperadrenocorticism were treated respectively). Congestive heart failure was encountered as
with transsphenoidal hypophysectomy resulted in five a transient problem in 4/19 cats that recovered from the
cats showing complete resolution of the disease. Four of surgery; all four cases occurred prior to implementing a
these cats had concurrent diabetes mellitus, two of which reduction in volume of intravenous fluid delivered as part
showed increased insulin responsiveness after surgery. of the postoperative protocol. Two cats developed paresis
A few case reports exist for the treatment of feline acro­ of the left orbicularis oculi muscle, which resolved in the
megaly with transsphenoidal hypophysectomy. Prior to surviving cat. Cardiac arrest occurred in one cat postop­
surgery, one patient was an insulin‐resistant diabetic that eratively at time of jugular catheter placement, which was
was still exhibiting clinical signs despite receiving 25 U of successfully revived and made an uneventful recovery.
insulin (Levemir® Novo Nordisk) four times per day. One cat developed a left pelvic limb monoparesis, which
Three weeks after surgery, the patient no longer required improved but did not resolve. Palatal wound breakdown
insulin therapy and up to one year later the patient’s IGF‐1 was not encountered. This large case series suggests that
and GH concentrations were within normal limits. hypophysectomy as a treatment for feline acromegaly
In another single case report, a 13‐year‐old male cas­ results in a high incidence of diabetic remission and reso­
trated domestic shorthair was treated for acromegaly with lution of acromegaly.
transsphenoidal hypophysectomy. The patient had a his­ An alternative procedure, cryohypophysectomy, has
tory of insulin‐resistant diabetes mellitus (15 units of glar­ been reported in a small number of cats but the proce­
gine BID) and was diagnosed with acromegaly via elevated dure has been less effective and results in a higher
IGF‐1 (447 nmol/L) and visualization of a pituitary mass complication rate.