Relationship among insulin resistance, growth hormone, and insulin-like growth factor I concentrations in diestrous Swedish Elkhounds.
BACKGROUND
In the dog, the normal estrous cycle includes a prolonged luteal phase. Progesterone stimulates local canine mammary growth hormone (GH) production, which may act systemically and contribute to insulin resistance. Swedish Elkhounds are predisposed to progesterone-related diabetes mellitus, and the relationship among insulin resistance, GH, and insulin-like growth factor I (IGF-I) is of particular interest.


OBJECTIVE
To study insulin resistance in relation to GH and IGF-I in nondiabetic Swedish Elkhounds during diestrus. We also assessed whether alterations in these hormones could predict diestrus-linked diseases and all-cause mortality.


METHODS
Eighty-four privately owned female intact Swedish Elkhounds >4 years of age.


METHODS
Blood sampling and clinical examination during luteal phase, with a follow-up questionnaire after 20 months. Insulin resistance was calculated by homeostasis model assessment (HOMA-IR).


RESULTS
In multivariable regression analysis, GH was positively associated with HOMA-IR (P = .009). An increase in GH of 1 ng/mL was associated with a 12.7% increase in HOMA-IR. Moreover, C-peptide was positively associated with IGF-I (P = .04), and an increase in C-peptide of 0.1 ng/mL was associated with a 6.9% increase in IGF-I. Structural equation modeling supported these results. Twenty-three animals were found to have previously unrecognized mammary masses and had higher GH (P < .0001) and IGF-I (P = .007) than dogs without mammary masses (n = 61). There was no association between high GH and IGF-I concentrations at sampling and future mammary masses.


CONCLUSIONS
We showed that GH was strongly associated with insulin resistance in older Swedish Elkhounds during diestrus.
E M
EM
Strage
M S
MS
Lewitt
J M
JM
Hanson
U
U
Olsson
F
F
Norrvik
I
I
Lilliehöök
B S
BS
Holst
T
T
Fall
D000818:Animals; D004031:Diestrus / Q000097:blood / Q000502:physiology*; D004283:Dog Diseases / Q000209:etiology / Q000503:physiopathology; D004285:Dogs / Q000097:blood / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000097:blood* / Q000502:physiology; D007333:Insulin Resistance / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000502:physiology
D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone