equine endocrinology group

Question 1

why does hyperinsulinemia cause laminitis?

Answer 1

we dont know

most popular theory is that hyperinsulinemia induces inappropriate stimulation of insulin-like growth factor-1 receptors on laminar epidermal cells. Decreased lamellar perfusion and altered energy regulation have also been considered

Question 2

Do horses with pituitary pars intermedia dysfunction (PPID) develop hyperinsulemia associated laminitis?

Answer 2

Yes,

_HAL is detected in approximately 30% of horses with PPID_4 and

it is recommended that horses greater than 10 years of age should be tested for PPID as well as ID.

Question 3

Insulin dysregulation can occur with

Answer 3

pregnancy,

EMS

starvation,

systemic illness

PPID?

Question 4

which test is recommended for insulin dysregulation?

Answer 4

Two-step approach

1. Resting (basal) insulin concentrations: A single blood sample is collected with the horse in the fed state (hay or pasture, but not grain), and plasma/serum insulin concentrations are measured to detect resting hyperinsulinemia.

IDEALLy always perform dyn test but ok if not much money

IF NEGATIVE:

2. Dynamic test: either or

• insuline tolerance: if negativ—–>>>>>>>>>
• oral sugar test (fasting, then 0,45ml corn sirup/kg

Question 5

Can one induce laminitis by performing dynamic insulin tests?

Answer 5

It has been the collective experience of the EqEndocrineGroup that dynamic tests cause

only transient alterations in glucose and insulin concentrations

and

do not induce laminitis.

Question 6

Initial diet for obese EMS horses

Answer 6

hay w low NSC content at 1.5% of current body weight

Select hay with NSC content < 10% as-fed if available.

soak hay for 60 mins in cold water

maintain until 5/9

Question 7

exercise in horses with ID dysregulation

Answer 7

previously laminitic horses with recovered and stable hoof laminae:

• low intensity exercise on a soft surface
• (fast trot to canter unridden; or heart rates 130-150 bpm)
• for >30 minutes, >3 times per week

non laminitic:

• low to moderate intensity exercise > 5 times per week
• such as canter to fast canter (ridden or unridden)
• w heart rates of 150- 170 bpm for >30 minutes
• OR
• 15 minutes of moderate trotting (with 5 min walking to warm up and warm down) 5 times per week also significant effect

Question 8

how do i know if the new diet helps in reducing insulin dysregulation?

Answer 8

postprandial insulin concentrations provide useful information on the individual horse’s response to their new diet and indirectly, the risk of laminitis developing.

2 hours after hay feeding

or

1hr grazing, 1h break and then test

Question 9

which time of the year are insulin concentrations physiologically higher?

Answer 9

winter

Question 10

– Algorithm for management of insulin dysregulation and pituitary pars intermedia dysfunction

Answer 10

Question 11

When is medical therapy indicated in EMS?

Which meds and why??

Answer 11

non-responders to management

• High-dose levothyroxine: synthetic T4

use when weight loss resistance, or accelerate weight loss in acute laminitis

• Sodium-glucose co-transporter 2 (SGLT2) inhibitors
  
  • inhibit the reuptake of gl from the glomer filtrate
  • contraindic: marked hypertriglyc

use when horses are affected by laminitis and severe ID

• Metformin hydrochloride
  
  • inhibits hepatic gluconeogenesis
  • opposes action of glucagon

use when persistent hyperinsulinemia despite management

Question 12

WHat is PPID?

Answer 12

Pituitary pars intermedia dysfunction

slowly progressive degenerative disease of

hypothalamic dopaminergic neurons.

>>> Loss of dopaminergic inhibitory control of

>>> pars intermedia (PI) melanotropes +++

>>> hyperplasia and adenoma formation in the Palnt

Melanotropes produce increased amounts of pro-opiomelanocortin, a large prohormone that is subsequently cleaved into smaller peptides,

including adrenocorticotropic hormone (ACTH).

Question 13

PPID prevalence?

Answer 13

only risk factor is age

prevalence increases to 30% in equids over 30 years

Question 14

early signs of PPID

Answer 14

Pathognomonic Hypertrichosis, firstly locally

Loss of Topline Musculature

Lethargy

Abnormal sweating

Suspensory Ligament laxity

Laminitis

regional adiposity

later frequent corneal ulcers…

infertility

Question 15

Laboratory findings that may accompany PPID

Answer 15

Hyperglycemia ▪ Hyperinsulinemia ▪ Hypertriglyceridemia ▪ High fecal egg count

Question 16

which test should be the first line for PPID testing?

which other tests are there?

Answer 16

• TRH stimulation test = first line test for suspected early-stage PPID
• baseline ACTH

OTHER POTENTIALLY SUPPORTIVE TESTS

▪ Overnight dexamethasone suppression test

▪ MRI specific for pars intermedia enlargement

Question 17

can TRH stim test be carried out on the same day as OST?

Answer 17

TRH testing can be performed immediately before an oral sugar test (OST)

but do not perform within 12 hours after an OST

or within 12 hours afetr grain feeding

Question 18

which values indicate that PPID is less likely?

Answer 18

Dec-June: <15 // < 40 not sure

july and november: <15// <50 not sure

august <20 // <75 not sure

sept-oct:<30 // <90 not sure

Question 19

When after initiation of treatment should PPID status be reassessed?

Answer 19

Evaluate clinical signs and

baseline ACTH

1-3 months after starting treatment,

and then every 6-12 months

Question 20

if horse is positive for PPID, what else should be tested for?

Answer 20

Assessment for insulin dysregulation

prevalence for ID: 1/3 of PPID cases

Question 21

PPID testing in stress and pain?

Answer 21

don’t take baseline values:

• within 30 minutes of trailering,
• if an animal that is visibly excited
• severe pain

you can still test (TRH and baseline) in case of

• Low to moderate pain > 24 hours duration
• laminitis, but it is ideal to postpone until severe pain is controlled.

Question 22

Sedation and PPID testing?

Answer 22

avoid diagnostic testing for PPID and insulin status within 24-48 hours of sedation.

has substantial impact!!