Spontaneous primary hypothyroidism in 7 adult cats

Abstract

BackgroundNaturally occurring hypothyroidism in adult cats is rare, with only 4 cases reported.ObjectivesTo describe the historical, clinical, laboratory, and scintigraphic features of adult cats with spontaneous hypothyroidism.AnimalsSeven adult cats referred for suspected hypothyroidism.MethodsProspective case series. We collected data on cats’ signalment, clinical signs, results of physical examination, routine laboratory and thyroid hormone testing, and thyroid imaging (thyroid scintigraphy or ultrasound). We subsequently treated cats with levothyroxine and evaluated their response to treatment.ResultsCats ranged from 3.5 to 11 years, with no apparent breed predilection; 6/7 cats were male. Only 2/7 cats were initially tested because of signs of hypothyroidism (hair‐coat changes, lethargy, obesity); others were tested for routine thyroid monitoring or palpable thyroid nodules. Four were azotemic (serum creatinine, 2.2‐3.4 mg/dL). Six of the cats had low serum thyroxine (T4) and free T4 (fT4) concentrations, whereas all 7 cats had high thyroid‐stimulating hormone (TSH) concentrations. In 6/7 cats, thyroid scintigraphy revealed bilateral goiter with intense radionuclide uptake; imaging showed no visible thyroid tissue in the other. After levothyroxine treatment, serum concentrations of T4 and fT4 increased and TSH fell; high serum creatinine normalized in azotemic cats; and repeat imaging showed reduction in goiter size.Conclusions and Clinical ImportancePrimary hypothyroidism develops in adult cats, with a higher prevalence than previously thought. Most cats appear to develop a goitrous form of hypothyroidism associated with thyroid hyperplasia, whereas thyroid atrophy appears to be less common. With levothyroxine replacement, clinical and laboratory abnormalities improve or resolve.

Serum thyroxine and thyrotropin concentrations decrease with severity of nonthyroidal illness in cats and predict 30‐day survival outcome

“…[1][2][3][4]8,13 We could not . 33,34,36 Obviously, differentiating the cause of the high serum TSH concentrations (ie, NTIS vs hypothyroidism) is much more important in cats treated for hyperthyroidism that develop iatrogenic hypothyroidism, which is a common complication, 34,36 than in cats with naturally occurring hypothyroidism, which is a rare disorder. [32][33][34] Cats that died within 30 days of thyroid testing had lower serum T 4 , T 3 , and TSH concentrations than did the cats that survived, suggesting that these hormone test results could be used to predict short-term outcomes, as previously suggested for T 4 in cats with NTIS.…”

“…As in humans and dogs, recent studies have demonstrated the utility of serum TSH concentrations for diagnosing cats with iatrogenic and naturally occurring hypothyroidism. [31][32][33][34] However, only limited data on serum TSH concentrations have been reported in a small number of cats with NTIS associated with chronic kidney disease, in which serum TSH concentration were within the reference interval. 35,36 If cats with NTIS do occasionally develop high serum TSH concentrations, this finding could lead to an erroneous diagnosis of hypothyroidism, as reported in humans and dogs with NTIS.…”

Cluster of cases of congenital feline goitrous hypothyroidism in a single hospital

“…Feline hypothyroidism is most frequently an iatrogenic consequence of therapy for hyperthyroidism (Welches et al 1989). Spontaneous hypothyroidism is uncommon, with only 11 cases of adult-onset disease (Rand et al 1993, Blois et al 2010, Galgano et al 2014, Kent et al 2016, Peterson et al 2018 and approximately 65 cases of congenital hypothyroidism reported (Arnold et al 1984, Peterson 1989, Sjollema et al 1991, Tanase et al 1991, Jones et al 1992, Peterson et al 1994, Stephan & Schütt-Mast 1995, Schumm-Draeger et al 1996, Firth et al 2000, Tobias & Labato 2001, Mazrier et al 2003, Crowe 2004, Szabo & Wells 2007, Traas et al 2008, Quante et al 2010, McGhie & Thompson 2011, Lim et al 2014, Peterson 2015, Van Bergen et al 2016, Jacobson & Rochette 2018.…”

“…2016, Peterson et al . 2018) and approximately 65 cases of congenital hypothyroidism reported (Arnold et al . 1984, Peterson 1989, Sjollema et al .…”

Management and monitoring of hyperthyroid cats: a survey of Australian veterinarians

“…Hyperthyroidism, first described in cats in 1979, is the most common feline endocrinopathy in most developed nations. 1,2 Recognised options for management of feline hyperthyroidism include administration of radioiodine, chronic daily dosing with antithyroid medication (orally or transdermally) and surgical thyroidectomy. 1 More recently, an iodine-restricted prescription diet has become available in certain countries.…”