Pituitary disorders are being seen more and more commonly in practice, especially amongst our diabetic cats.

As nurses, it’s really important that we have an awareness of the common pituitary disorders that we see, the effects they have on the body, and how they are diagnosed and treated, in order to plan and deliver the best possible nursing care.

In this post, we’ll be looking at the three main pituitary disorders we see in practice - acromegaly, pituitary dwarfism and diabetes insipidus - and discussing their pathophysiology, clinical signs, diagnostics and treatment.

Stay tuned as we work together to plan nursing care for these patients!

Acromegaly

Feline acromegaly, or hypersomatotropism, is a common endocrinopathy seen in cats. It is characterised by the excessive release of growth hormone from a benign mass on the pituitary gland.

It is typically seen in senior cats aged >8 years, and male cats are diagnosed more frequently than females.

As growth hormone causes insulin resistance, diabetes mellitus not responsive to exogenous insulin is most commonly reported in acromegalic cats. We may also see changes to the patient’s body shape and facial conformation associated with the increased growth hormone levels (they can also have very tough skin, which makes venepuncture quite challenging!)

Clinical Signs

The main clinical signs we see with acromegaly are those of diabetes mellitus, since insulin-resistant diabetes is typically seen. So these patients often present initially with PU/PD, polyphagia, weakness, lethargy +/- plantigrade posture. 

Diagnostics

Generally, diabetes mellitus is diagnosed first, and as patients demonstrate poor response to insulin, we begin to suspect acromegaly. In fact, up to 25% of diabetic cats have acromegaly.

We confirm the diagnosis of acromegaly with blood insulin-like growth factor (IGF-1) levels, and potentially growth hormone levels depending on your location (they are not easily measurable in the UK so I’ve not measured those myself!).

Advanced imaging of the head (CT or MRI) demonstrates the presence of a pituitary mass.

Treatment and Nursing Care

Treatment options include either medical mangement, radiation therapy or surgery. Generally, surgical management is preferred.

Commonly, surgical management is achieved with a hypophysectomy (complete removal of the pituitary gland). This is generally performed via an intraoral approach through the sphenoid bone in the roof of the mouth. This is a complex surgery with patients requiring intensive monitoring in the postoperative period.

When we remove the entire pituitary gland, we also affect the release of other hormones - essentially, we will make these patients hypothyroid and Addisonian and they will require lifelong treatment for these conditions, and it is important that this is discussed with clients before they make decisions regarding treatment. These patients will also have diabetes insipidus in the initial post-operative period and often require a period of DDAVP supplementation, though this may be able to be discontinued in time.

Nursing care includes careful monitoring of vital parameters and glucose levels, fluid balance, urine specific gravity and output alongside nutrition, pain, neurological status and general nursing care. Once the patient has been supported through surgical recovery, their diabetes should resolve and they will require long-term monitoring and care of their other endocrine disorders.

Pituitary Dwarfism

Hyposomatotropism is a deficiency of growth hormone. It is a very rare condition but is usually congenital, and German Shepherd Dogs are overrepresented.

Clinical Signs

Clinical signs of hyposompatotropism include small stature, poor weight gain and body condition score, and a juvenile hair coat.

Depending on the form of dwarfism seen, we may also see other changes to the patient’s body conformation. Pituitary dwarfism may be either proportionate or disproportionate, depending if only growth hormone levels are deficient, or if additional endocrinopathies are present (most commonly hypothyroidism).

Disproportionate dwarfism patients often have larger, wider skulls and a smaller body.

Diagnostics

Hyposomatotropism is diagnosed by measuring IGF-1 levels, and by ruling out other causes of small body stature, such as hypothyroidism and portosystemic shunts. Common tests for this include T4/TSH levels, bile acid stimulation test and ammonia levels, and an abdominal ultrasound.

Treatment

Treatment includes management with growth hormone supplementation, and if other endocrinopathies such as hypothyroidism are present, supplementation with levothyroxine.

Diabetes Insipidus

Diabetes insipidus, or “water diabetes” has nothing to do with glucose levels, and is all about water balance in the body.

There are 2 forms of diabetes insipidus - central and nephrogenic:

• Central DI occurs in the pituitary gland and is characterised by a lack of antidiuretic hormone (ADH) production.

• Nephrogenic DI occurs in the kidneys and is characterised by a lack of ADH activity in the kidney.

Whilst central diabetes insipidus is a primary (idiopathic) condition, nephrogenic DI is usually seen secondary to other diseases.

Clinical Signs

As ADH is responsible for concentrating urine by reabsorbing water in the kidney, if ADH either is not produced or cannot work effectively, urine remains dilute.

This results in marked polyuria and, to compensate for the increased urinary losses, polydipsia.

Patients with DI have a urine output exceeding 66ml/kg/day and a water intake exceeding 100ml/kg/day.

Diagnosis and Treatment

DI is diagnosed by exclusion - after eliminating other causes of PU/PD. This generally consists of:

• Routine biochemistry and haematology

• Urine analysis

• +/- Ionised calcium levels

• +/- T4/TSH levels

• +/- ACTH stimulation test

• +/- thoracic and abdominal imaging

Water deprivation tests are no longer recommended or used as they carry significant risks of dehydration; instead, we generally trial treatment with DDAVP (synthetic ADH) and assess the patient’s response.

The most important nursing consideration for these patients is ensuring they have water freely available at all times and regular toilet walking due to their severe PU/PD. It is also vital that clients are made aware that these patients will be polydipsic and require water to be freely available always. They must not try and restrict the patient’s water intake in response to their polydipsia, as this can result in severe dehydration.

So that’s an overview of the most common pituitary disorders we see in the clinic - as you can see, they have a real variety of signs, and there is a lot of potential for us to do lots with these patients, particularly our acromegalic cats.

Have you ever seen a patient with acromegaly? DM me over on Instagram and let me know!

References:

1. Merrill, L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell.