ENDOCRINOLOGY
Treatment Options for
Pituitary Dependent
Hyperadrenocorticism
By Dr L L van der Merwe , BVSC (MMedVet(Med)
And by dr Marlies Bohm, BVSc DSAM MMedVet(Med) DipECVIM-CA
PDH is the most common (82%) form of canine hyperadrenocorticism. Any treatment whether surgical or medical will require life-long medication and some hormone monitoring
A. Surgical resection of the pituitary tumour
(trans-sphenoidal hypophysectomy)
Surgery is the treatment of choice for humans. Bjorn
Meij of Utrecht pioneered the surgery (trans-sphenoidal hypophysectomy) and has operated on > 200
dogs and cats. With surgery the cause of the problem is addressed whereas with medical management
control is aimed at limiting the effects of the pituitary
tumour.
If your patient is starting to show neurological signs
and the CT/MRI indicate that the tumour is still operable then surgery is really your best choice. If your
patient is relatively young you could also consider surgery – because if he is expected to survive for many
years assuming his Cushing’s is controlled then it
means there are many years for the pituitary tumour
to grow and ultimatly causes neurological disease.
There are some pituitary tumours that are too large to
be removed. The bigger the tumour the greater the
risk associated with surgery and the lower the chance
that the tumour can be completely removed.
Dr Meij is prepared to fly out from Utrecht and perform the surgery at Onderstepoort. The post op period is tricky and requires constant supervision in ICU.
You will need to cover the costs of Dr Meij’s flights, his
professional fee for the surgery and Onderstepoort’s
fee. The last case cost the owners approx. R50 000.
(Feb 2014). Contact Dr Marlies Bohm (marlies@wol.
co.za) if you are considering this option - she organised this for a patient recently.
Prognosis:
92% of a group of 150 dogs survived surgery and the
immediate post-operative period and the survival
rates are expected to be even higher in resent cases,
as the technique was refined. In 9/150 (6%) dogs the
surgeon wasn’t able to remove all the tumour.
• In 25% of dogs signs of Cushing’s recurred 6
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Issue 06 | DECEMBER 2015 | 16
•
weeks – 56 months (median 18 months) post operatively.
75% of patients stayed free of signs of Cushing’s
and died of unrelated diseases. These dogs lived
for an average of 28 months (range 2-87 months)
after surgery. This doesn’t sound terribly long, but
Cushing’s typically affects middle aged to elderly
dogs that have a limited life expectancy in any
case.
Post-operative treatment:
All dogs will need thyroid hormone supplements and
hydrocortisone post operatively. The hydrocortisone
dose is slowly weaned down to a fairly standard lowest effective dose.
• The thyroid hormone dose needs to be adjusted
to the individual dog.
• The hydrocortisone dose is increased during
times of stress (illness, travel, kennelling, hunting).
• Dogs may need DDAVP (a synthetic form of antidiuretic hormone, vasopressin) transiently in the
immediate post-operative period.
Based on 150 operated dogs: 47% of dogs can stop
taking DDAVP within 2 weeks of surgery and an additional 31% could stop eventually. The remaining 22%
needed it for life.
B. Treatment with mitotane (Lysodren = o’pDDD)
Mitotane, the first effective treatment for Cushing’s,
destroys the cortisol producing cells in the adrenal
gland. Lysodren is not licensed for use in SA and a
section 21 application is required.
Induction :
Lysodren dose - 50mg/kg oid
• Start induction on a Thursday / Friday so that the
chances of drama on a weekend are diminished
as the process generally takes 5 – 10 days.
• The pills are given in the morning after breakfast
has been eaten.
• If the dog fails to wolf down his breakfast as nor-