PlasmaACTHPrecursors in Cats with Pituitary‐Dependent Hyperadrenocorticism

Abstract

Background: Diagnosis of pituitary-dependent hyperadrenocorticism (PDH) in cats is challenging because there is no specific diagnostic test.Hypothesis/Objective: The determination of plasma ACTH precursor (POMC and pro-ACTH) concentration might facilitate the diagnosis of PDH in cats. The aim of the study was to evaluate prospectively the plasma concentrations of ACTH precursors in a small cohort of cats with PDH and to estimate the value of this approach for diagnosis.Animals: Four groups of cats were included: group 1 (cats with PDH), group 2 (cats with diabetes mellitus but not hyperadrenocorticism (HAC)), group 3 (cats with diabetes mellitus and confirmed acromegaly but not HAC), and group 4 (healthy cats).Methods: PDH diagnosis was based on clinical data, low-dose dexamethasone suppression test (LDDST), and adrenal and pituitary gland computed tomography (CT) scan. For groups 2, 3, and 4, hyperadrenocorticism was excluded by LDDST or urine cortisol:creatinine ratio (UCCR). An immunoluminometric assay was used to determine plasma concentrations of ACTH precursors in the 4 groups of cats.Results: Group 1 contained 9 cats (enlarged pituitary gland in 7/9). Plasma ACTH precursor concentrations ranged from <53 to >1010 pmol/L with 8/9 concentrations ! 229 pmol/L. Groups 2, 3, and 4 included 13, 7, and 13 cats, respectively. Plasma ACTH precursor concentrations ranged from <53 to 96 pmol/L in group 2, <53 to 72 pmol/L in group 3, and <53 to 99 pmol/L in group 4.Conclusion and Clinical Importance: High plasma concentration of ACTH precursors in cats (>100 pmol/L) is highly suggestive of PDH.

Hyperadrenocorticism in Cats

“…Thirty-eight of these cats were from our series, and 13 were from the literature ( However, 17 cats with PDH (38%) had plasma endogenous ACTH concentrations in excess of 450 pg/mL (range, 487 to 3850 pg/ mL; mean, 1002 pg/mL ± a SD of 731). Precursors of ACTH were above the reference range in eight of nine cats that had PDH (Benchekroun et al, 2012). Is it that their pituitary tumors produce more ACTH, is the assay less reliable in cats, is the assay more reliable in cats, is the assay also measuring precursors in the cat, or is there some other explanation?…”

“…A visible mass (5 to 11 mm in greatest diameter) was identified in 34 cats (70%; Fig. Thirteen of 22 cats (59%) from three different studies utilizing CT scans had a visible mass (Goossens et al, 1995;Meij et al, 2001;Benchekroun et al, 2012); in the UC Davis series, visible masses were identified in six of nine cats evaluated with CT and four of six evaluated with MRI. Thirteen of 22 cats (59%) from three different studies utilizing CT scans had a visible mass (Goossens et al, 1995;Meij et al, 2001;Benchekroun et al, 2012); in the UC Davis series, visible masses were identified in six of nine cats evaluated with CT and four of six evaluated with MRI.…”

Clinical Findings, Diagnostic Test Results, and Treatment Outcome in Cats with Spontaneous Hyperadrenocorticism: 30 Cases

“…Serum total thyroxine concentrations were interpreted using the reference ranges provided by the individual laboratories. Plasma endogenous ACTH concentrations <10.0 pg/mL were considered compatible with ADH and concentrations >12.0 pg/mL were considered compatible with PDH …”

“…Spontaneous hyperadrenocorticism (HAC) is a consequence of abnormally increased functional activity of the adrenal cortex. This disease classically (and most commonly) is associated with hypercortisolism in small animal companion species . However, although well described in dogs, fewer than 100 cats with HAC have been described in the peer‐reviewed veterinary literature, with the largest case series describing only 10 patients .…”

Trilostane Therapy for Treatment of Spontaneous Hyperadrenocorticism in Cats: 15 Cases (2004–2012)

“…Measurement of IGF‐1 was not performed in any of these cats; however, 8/15 of the cats in this case report were presented with skin fragility syndrome and had cortisol function testing results consistent with HAC. A prospective study evaluating plasma ACTH precursors in cats with PDH revealed that most cats had increased concentrations of plasma ACTH precursors, compared with healthy cats, or cats with DM with or without acromegaly . Precursor measurement might aid in differentiating PDH from acromegaly in conjunction with IGF‐1 levels and clinical signs, if a suspected cushingoid cat does not have fragile skin.…”