Serum N-Terminal Type III Procollagen Propeptide: An Indicator of Growth Hormone Excess and Response to Treatment in Feline Hypersomatotropism

Hypersomatotropism and Other Causes of Insulin Resistance in Cats

True insulin resistance should be differentiated from management-related difficulties (eg, short insulin duration, inappropriate insulin injection, inappropriate storage). Hypersomatotropism (HST) is the number one cause of insulin resistance in cats, with hypercortisolism (HC) occupying a more distant second place. Serum insulinlike growth factor-1 is adequate for screening for HST, and screening at the time of diagnosis, regardless of presence of insulin resistance, is advocated. Treatment of either disease centers on removal of the overactive endocrine gland (hypophysectomy, adrenalectomy) or inhibition of the pituitary or adrenal glands by using drugs such as trilostane (HC), pasireotide (HST, HC) or cabergoline (HST, HC).

Efficacy of hypophysectomy for the treatment of hypersomatotropism-induced diabetes mellitus in 68 cats

Background

Hypersomatotropism (HST) is an increasingly recognized endocrinopathy in cats and is mostly described associated with diabetes mellitus (DM).

Objectives

To evaluate the efficacy and safety of transsphenoidal hypophysectomy in treating HST and DM in cats.

Animals

Sixty‐eight client‐owned cats with HST and DM treated by transsphenoidal hypophysectomy.

Methods

Retrospective cohort study. Medical records were reviewed for glycemic control and serum insulin‐like growth factor‐1 (IGF‐1) concentrations. Postoperative complications, death within 4 weeks, and proportion achieving diabetic remission were recorded. Survival times and DM‐free intervals were calculated.

Results

Fifty‐eight cats (85.3%) were alive 4 weeks postoperatively with 10 (15%) postoperative deaths. Complications included hypoglycemia (n = 9), electrolyte imbalance (n = 9), and transient congestive heart failure (n = 5). Fifty‐five cats (95% of 58 surviving cats [81% of all cats undergoing surgery]) had improved control of diabetes. Diabetic remission occurred in 41 cats (71% of 58 surviving cats [60% of all cats]) with insulin administration discontinued after a median of 9 days (range, 2‐120). Postoperative 4‐week serum IGF‐1 concentration nadir was significantly lower in cats achieving diabetic remission (median 20 ng/mL [15‐708] than those that did not (324 ng/mL [15‐1955]; P = .03). All cats received long‐term levothyroxine and hydrocortisone PO, alongside desmopressin (conjunctival) in 38 of 53 cats (72%). Recurrence of DM occurred in 5 of 41 cats (12%) after a median of 248 days (range, 84‐1232). Median survival time of all cats was 853 days (range, 1‐1740).

Conclusions and Clinical Importance

Transsphenoidal hypophysectomy is an effective treatment for cats with HST and DM, with a long‐term outcome that compares favorably to existing options.

Radiotherapy and pasireotide treatment of a growth hormone producing pituitary tumor in a diabetic dog

An 8-year-old castrated male border terrier dog was diagnosed with acromegaly resulting from a growth hormone secreting pituitary tumor. Sixteen daily fractions of radiation therapy were delivered followed, approximately 1 year later, by administration of pasireotide. The aforementioned treatment was considered effective and should be further evaluated in similar cases.

Time spent with cats is never wasted: Lessons learned from feline acromegalic cardiomyopathy, a naturally occurring animal model of the human disease

BACKGROUND

In humans, acromegaly due to a pituitary somatotrophic adenoma is a recognized cause of increased left ventricular (LV) mass. Acromegalic cardiomyopathy is incompletely understood, and represents a major cause of morbidity and mortality. We describe the clinical, echocardiographic and histopathologic features of naturally occurring feline acromegalic cardiomyopathy, an emerging disease among domestic cats.

METHODS

Cats with confirmed hypersomatotropism (IGF-1>1000ng/ml and pituitary mass; n = 67) were prospectively recruited, as were two control groups: diabetics (IGF-1<800ng/ml; n = 24) and healthy cats without known endocrinopathy or cardiovascular disease (n = 16). Echocardiography was performed in all cases, including after hypersomatotropism treatment where applicable. Additionally, tissue samples from deceased cats with hypersomatotropism, hypertrophic cardiomyopathy and age-matched controls (n = 21 each) were collected and systematically histopathologically reviewed and compared.

RESULTS

By echocardiography, cats with hypersomatotropism had a greater maximum LV wall thickness (6.5mm, 4.1-10.1mm) than diabetic (5.9mm, 4.2-9.1mm; Mann Whitney, p<0.001) or control cats (5.2mm, 4.1-6.5mm; Mann Whitney, p<0.001). Left atrial diameter was also greater in cats with hypersomatotropism (16.6mm, 13.0-29.5mm) than in diabetic (15.4mm, 11.2-20.3mm; Mann Whitney, p<0.001) and control cats (14.0mm, 12.6-17.4mm; Mann Whitney, p<0.001). After hypophysectomy and normalization of IGF-1 concentration (n = 20), echocardiographic changes proved mostly reversible. As in humans, histopathology of the feline acromegalic heart was dominated by myocyte hypertrophy with interstitial fibrosis and minimal myofiber disarray.

CONCLUSIONS

These results demonstrate cats could be considered a naturally occurring model of acromegalic cardiomyopathy, and as such help elucidate mechanisms driving cardiovascular remodeling in this disease.

Time spent with cats is never wasted: Lessons learned from feline acromegalic cardiomyopathy, a naturally occurring animal model of the human disease

Background

In humans, acromegaly due to a pituitary somatotrophic adenoma is a recognized cause of increased left ventricular (LV) mass. Acromegalic cardiomyopathy is incompletely understood, and represents a major cause of morbidity and mortality. We describe the clinical, echocardiographic and histopathologic features of naturally occurring feline acromegalic cardiomyopathy, an emerging disease among domestic cats.

Methods

Cats with confirmed hypersomatotropism (IGF-1>1000ng/ml and pituitary mass; n = 67) were prospectively recruited, as were two control groups: diabetics (IGF-1<800ng/ml; n = 24) and healthy cats without known endocrinopathy or cardiovascular disease (n = 16). Echocardiography was performed in all cases, including after hypersomatotropism treatment where applicable. Additionally, tissue samples from deceased cats with hypersomatotropism, hypertrophic cardiomyopathy and age-matched controls (n = 21 each) were collected and systematically histopathologically reviewed and compared.

Results

By echocardiography, cats with hypersomatotropism had a greater maximum LV wall thickness (6.5mm, 4.1–10.1mm) than diabetic (5.9mm, 4.2–9.1mm; Mann Whitney, p<0.001) or control cats (5.2mm, 4.1–6.5mm; Mann Whitney, p<0.001). Left atrial diameter was also greater in cats with hypersomatotropism (16.6mm, 13.0–29.5mm) than in diabetic (15.4mm, 11.2–20.3mm; Mann Whitney, p<0.001) and control cats (14.0mm, 12.6–17.4mm; Mann Whitney, p<0.001). After hypophysectomy and normalization of IGF-1 concentration (n = 20), echocardiographic changes proved mostly reversible. As in humans, histopathology of the feline acromegalic heart was dominated by myocyte hypertrophy with interstitial fibrosis and minimal myofiber disarray.

Conclusions

These results demonstrate cats could be considered a naturally occurring model of acromegalic cardiomyopathy, and as such help elucidate mechanisms driving cardiovascular remodeling in this disease.