EXPLANATION OF ELEVATED IGF-1 3 Oct 2015

EXPLANATION OF ELEVATED IGF-1     3 Oct 2015
QUESTION--I have a patient with an elevated igf-1 level that I would like to submit a question to endotext ask an expert. The patient is a 34 year old female with dm2 diagnosed at age 24, obesity, seizure d/o, and autism. She had an igf-1 checked in 2011 and it was found to be elevated.
History cannot be obtained from patient due to her autism but she attends a day program and does not have any complaints.
Meds:
Metformin
abilify
zoloft
topamax
Simvastatin
Klonopin
Provera im q3 months

Wt Readings from Last 3 Encounters:
06/18/15 : 143.3 kg (315 lb 14.7 oz)
Physical Exam
Constitutional: She is oriented to person, place, and time. She appears not dehydrated. Non-toxic appearance. No distress.HENT:Head: Normocephalic and atraumatic. +frontal bossing
Cardiovascular: Normal rate and regular rhythm.
Pulmonary/Chest: Breath sounds normal. No respiratory distress.
Musculoskeletal: She exhibits no edema.
Large hands
Neurological: She is alert and oriented to person, place, and time.
Skin: Skin is warm and dry.
7/31/12  igf-1 624 ng/ml
2/17/12  igf-1 682 ng/ml
11/11/11  igf-1 724 ng/ml
10/24/11  igf-1 828 ng/ml
Glucose suppression tests
8/21/15-growth hormone baseline 0.3 ng/ml, 1 hour <0.1 ng/ml, 2 hr 0.1 ng/ml
7/31/12-growth hormone  baseline <0.1 ng/ml,  1 hour <0.1 ng/ml,   2 hour  N/A
2/17/12-growth hormone baseline <0.1 ng/ml,   1 hour 0.5 ng/ml,  2 hour 9.3 ng/ml
12/7/11-growth hormone baseline 2.4 ng/ml,  1 hour 1.4 ng/ml,  2 hour 0.2 ng/ml

GLUC 92 03/03/2015
GLUC 83 10/12/2014
GLUC 91 02/14/2014
GLUC FAST 79 06/02/2014
GLUC FAST 94 01/22/2009
GLUC FAST 156 04/16/2005
HGBA1C 6.1 03/03/2015
HGBA1C 6.1 10/12/2014
HGBA1C 5.9 06/02/2014
MICROALB 7.8 10/12/2014
MICROALB 3.4 04/03/2014
MICROALB 3.6 07/22/2013
MICROALBUMIN/CREATININE 3.1 10/12/2014
MICROALBUMIN/CREATININE 2.4 04/03/2014
MICROALBUMIN/CREATININE 1.9 07/22/2013
CHOL 190 03/03/2015
TRIG 117 03/03/2015
HDL 51 03/03/2015
LDL CALC 116 03/03/2015
LDL 145 10/12/2014
CHOL/HDL 3.7 03/03/2015
TRIGLYCERIDE, NONFASTING 114 10/12/2014
CREAT 1.02 05/19/2015
MRI of pituitary 4/2012-Pituitary gland was heterogenous .
MRI of pituitary 5/19/15 -Pituitary had suggestion of a tiny left microadenoma
I would like to know how to interpret the discordant results with the elevated igf-1 and the growth hormone that suppresses on the 75 gm glucose tolerance test. Robert.S.Heymann@kp.org
RESPONSE-Discordance in serum IGF-1 and GH is a well-recognized phenomenon which was encountered more commonly in the past, prior to lowering of the thresholds of the GH nadir to glucose for diagnosis.
According to the results submitted, the patient had one unsuppressed 2 hour GH to glucose in 2012 (9.3), but all other tests show suppression of GH to <0.1 ng/ml. The normal ranges of IGF1 are not given, but assuming they are indeed elevated one must consider other causes of this. One possibility is severe insulin resistance, as the elevated insulin levels may themselves elevate IGF1 levels, in a patient with very marked obesity.
Apart from this, as thyroid dysfunction can also lead to discordance, please check and correct any thyroid dysfunction in her. The other pituitary hormones, especially prolactin, might shed further light on her pituitary status.
Several exogenous factors can suppress pituitary growth hormone release. High fat mass, which leads to increased free fatty acid and insulin resistance, can cause lowering of IGF-binding protein-1 and a relative increase in free IGF-1. This can lead to suppressed GH release from the pituitary, and might explain the low baseline GH in this lady. However, we would still expect the IGF1 to be normal; total IGF1 levels, as usually measured, should not change. However, in the absence of significant clinical features, and the clear suppression of GH after glucose, and the absence of a pituitary macroadenoma, I would consider acromegaly extremely unlikely.Kavinga Gunawardane, MD