7: ENDOCRINOLOGY

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CHAPTER 7 ENDOCRINOLOGY

Diabetes
Thyroid disorders
Obesity

DIABETES

A GP with a list of 2000 patients might expect to have 50 patients with diabetes, 10–15 of whom will be receiving insulin at any one time. Diabetes occurs because of lack of insulin, or resistance to its action, and is diagnosed by raised blood sugars.

Tip

Active case-finding and organised screening of selected groups is the key to diagnosis.

Risk factors in diabetes

The following factors put people at increased risk of developing diabetes:

• >65 years old
• Asian or Afro-Caribbean origin
• obesity, particularly abdominal obesity
• a family history of diabetes or cardiovascular disease
image

Diagnosis

Patients are often asymptomatic and may be diagnosed during routine or opportunistic screening.

History.

Patients with the following symptoms should be tested for diabetes:

• thirst, polyuria and weight loss
• recurrent infections, especially skin infections
• neuropathic symptoms, e.g. pain, numbness and paraesthesiae
• marked visual acuity changes
• unexplained symptoms, e.g. lassitude.

Tip

Diabetes is defined by WHO criteria, using venous samples, as:

• a fasting blood glucose level of >7.0 mmol/l, or
• a random plasma glucose level of >11.1 mmol/l.

In asymptomatic patients the measurements should be duplicated on another day before the diagnosis is made.

Investigations

Patients with a fasting plasma glucose between 6.1 and 7.0 mmol/l have impaired fasting glycaemia and need an oral glucose tolerance test.

The oral glucose tolerance test

• The patient should not have smoked and should have had a normal carbohydrate intake for the previous 3 days.

– After an overnight fast, give 75 g of oral glucose (350 ml of Lucozade can be used).
– Measure blood glucose 2 hours later.

• If >11.1 mmol/l, the patient is diabetic.
• If >7.8 and <11.1 mmol/l, the patient has impaired glucose tolerance.
• If <7.8, the patient has normal glucose tolerance.

Patients with impaired fasting glycaemia and impaired glucose tolerance should have annual follow-up with fasting blood glucose measurement.

Management

Referral.

At the time of diagnosis, if the patient is ill, ketonuria is present or if the blood glucose is more than about 25 mmol/l, immediate referral should be arranged.

Admit all children and pregnant women.

Aims of diabetic care

• To keep the patient well and symptom-free.
• To keep the fasting blood glucose below 6.7 mmol/l, the maximum blood glucose below 10 mmol/l and the level 2 hours after a meal below 6.7 mmol/l. (It is generally believed that good diabetic control prevents the development of long-term complications.)
• To avoid fasting glycosuria.
• To maintain the HbA1c below 7%.
• To minimise the risk of cardiovascular disease by vigorously treating hypertension (<130/80) and hypercholesterolaemia (reduce total cholesterol by 25% or to <4 mmol/l, whichever is the lower value) in conjunction with the diabetes. All diabetics should be prescribed aspirin 75 mg od if aged >50 and a statin, e.g. simvastatin 40 mg od if aged 40–80, or if younger and total serum cholesterol >5 mmol/l.
• To detect complications early, in order to reduce:

– angina, MI and cerebrovascular disease
– foot ulceration and limb amputation due to peripheral vascular disease and diabetic neuropathy
– visual loss due to diabetic retinopathy
– renal failure due to diabetic nephropathy.

• To offer effective education.

General management.

Practice nurses and diabetes specialist nurses have a valuable role in sharing the management of the diabetic patient. Diabetes UK is the national association for diabetes (see p. 356) and offers excellent on-line advice to both patients and professionals.

Education

• Emphasise the importance of self-management.
• Advise against smoking.
• Self-monitoring:

– All type 1 (insulin-dependent diabetes mellitus (IDDM)) patients should measure their blood glucose (and, ideally, their urine for ketonuria). Teach home glucose monitoring using a blood glucose test meter. Testing should ideally be carried out before each main meal and before bed.
– Urine testing alone is satisfactory for older type 2 diabetics. The urine should be tested 2 hours after a meal. A series of three tests on one day per week is more useful than once-daily testing.

• Intercurrent illness:

Diabetes therapy (insulin or tablets) should never be reduced or omitted during intercurrent illness. Insulin-dependent diabetics usually require more insulin during intercurrent illness.

– Non-insulin-treated patients can occasionally become ketoacidotic during intercurrent illness and may require insulin therapy.
– The frequency of self-monitoring should be increased.
– Fluid intake should be increased.
– Daily carbohydrate intake should be maintained, as liquid if necessary.
– If the blood glucose is >13 mmol/l or the urine sugar is >2%, increase the insulin by 2–4 units per day until control is regained.
– Admit if the patient is vomiting and unable to take liquid or carbohydrate, or is ketoacidotic or dehydrated.

• Give advice on foot care. Look out for problems, e.g. corns, ingrowing toenails, bunions, and refer to podiatry if appropriate.
• Discuss the warning signs of hypoglycaemia (unsteadiness, difficulty in concentration, headache and tremulousness).
• Diet:

– Refer all newly diagnosed patients for dietary advice (practice nurse or dietician).
– Overweight patients need advice on calorie reduction (according to desired BMI).

Tip

The main dietary message for diabetics is to eat ‘healthily’. At least half of the energy intake should be made up of complex, fibre-rich carbohydrates. Intake of refined carbohydrate, fat, alcohol and salt should be low.

• Exercise: regular exercise should be strongly encouraged.
• Immunisations: offer influenza and pneumococcal vaccine to all diabetics.
• Driving: patients must notify the Driver and Vehicle Licensing Agency and their insurance company, unless their diabetes is controlled by diet alone.
• Free prescriptions: patients receiving treatment with either tablets or insulin are exempt from paying prescription charges.
• Occupation: hazardous jobs are no longer an option for patients with type 1 diabetes mellitus, e.g. police, armed forces.

Routine review.

The patient should be checked at least 6-monthly (either by the GP, practice nurse or hospital diabetic clinic).

Look at:

• The patient’s own records of blood or urine testing (self-monitoring).
• Fasting blood sugar HbAic.
• Weight/BMI (and discuss diet).
• Urine for protein. If present, send an MSU for MC&S, and check C&Es.

Refer to a nephrologist if there is persistent proteinuria or if the creatinine is raised >150 μmol/l. Tight hypertensive control is important. Proteinuria, rising BP and deteriorating renal function are indicators of nephropathy.

If proteinuria is absent, the urine should be checked for microalbuminuria (microalbuminuria precedes frank proteinuria, and antihypertensive treatment slows progression). If positive (>20 mg/l), the patient should be started on an ACE inhibitor, even if normotensive, to delay the onset of nephropathy.

Check annually:

• BP. Aiming to reduce to below 130/80 ideally.
• Visual acuity.
• Fundi (dilate pupils with 1% tropicamide). Fundoscopy and fundal photography can be performed by accredited opticians throughout the UK.
• Bloods:

– C&Es, to exclude renal failure
– serum cholesterol, triglyceride and HDL, aiming to reduce total cholesterol by 25% or to <4.0 mmol/l, whichever is the lowest, by the use of statins.

• Feet:

– pulses
– reflexes
– vibration and pinprick sensation
– evidence of ulceration, etc. – treat infection, arrange Doppler, refer urgently to specialised foot care team and consider referral for angiography.

Therapeutic management of type 2 diabetes mellitus

Tip

The primary treatment of type 2 diabetes is diet, with the aim of reducing excess weight and avoiding refined sugar.

Tablets and insulin should not be used before an adequate trial of diet alone (2–3 months), unless the patient is very ill or has a very high blood glucose (>25 mmol/l).

Start with metformin 500 mg od (decreases gluconeogenesis and increases peripheral utilisation of glucose), provided renal and hepatic function are normal. Metformin is particularly useful for overweight patients, as it is less likely to cause weight gain than the sulphonylureas. Increase the dose monthly as appropriate, to a maximum of 1 g bd. Add a sulphonylurea (see below) if control remains inadequate, e.g. gliclazide 40–80 mg od (augments insulin secretion), adjusted according to response up to a maximum of 160 mg bd. Warn the patient of the hazard of hypoglycaemia.

Consider other antidiabetic agents:

• Glitazones, e.g. rosiglitazone (reduce peripheral insulin resistance). Use as second-line therapy and in patients who are unable to tolerate metformin and sulphonylurea in combination or in patients in whom either metformin or a sulphonylurea is contraindicated.
• Nateglinide and repaglinide stimulate insulin release. Both may be given in combination with metformin. The latter may be given as monotherapy.
• Acarbose is an inhibitor of intestinal alphaglucosidases. It may be used alone or as an adjunct to metformin or to sulphonylureas.

If control remains poor despite attention to diet and tablets, insulin therapy should be considered.

Therapeutic management of type 1 diabetes mellitus.

Insulin doses are determined on an individual basis, by gradually increasing the dose but avoiding disabling hypoglycaemia. If the blood glucose is too high, increase the dose of insulin. If the blood glucose is too low, decrease it. Hypoglycaemia between 10 a.m. and lunchtime or between the evening meal and midnight is due to too much short-acting insulin in the morning or evening, respectively. Reduce the dose by 2–4 units.

Hypoglycaemia between 2 p.m. and the evening meal or during the night or before breakfast is due to too much long-acting insulin in the morning or evening, respectively. Reduce the dose by 4–6 units.

Hypoglycaemia.

Treat with oral glucose.

If the patient is unconscious, treat with glucagon 1 mg im, sc or iv, or glucose gel (e.g. Hypostop). Both can be issued to responsible relatives for emergency use.

Administration

Quality and Outcomes Framework for Diabetes

• Record body mass index.
• Achieve an HbA1c 7.5% or below.
• Record retinal screening.
• Record peripheral pulses.
• Test for neuropathy.
• Achieve a blood pressure of 145/85 or below.
• Test for microalbuminuria.
• Measure the creatinine.
• Treat microalbuminuria with an ACE inhibitor or A2 antagonist.
• Achieve a cholesterol of 5 mmol/l or below.
• Annual flu vaccination.
• Ask about depression.

THYROID DISORDERS

HYPOTHYROIDISM

Hypothyroidism is common, especially in elderly people in whom the presenting signs are often non-specific. The threshold for testing should therefore be low.

Diagnosis

• Serum thyroid stimulating hormone (TSH) is the best initial screening test, as a normal value virtually excludes hypo- and hyperthyroidism.
• If the TSH is high, measure free T4. If this is low, hypothyroidism is confirmed.
• In subclinical hypothyroidism the TSH is high but the free T4 is normal, and when to start T4 replacement is a matter of clinical judgement.
• Problems with interpreting thyroid function tests in the elderly usually result from non-thyroidal illness or drug treatment.

Management

Most cases of hypothyroidism, particularly in the elderly, can be managed by the GP. Refer those who are young or ill. Check for autoantibodies (their presence makes other autoimmune diseases more likely).

Treatment.

Treat with oral levothyroxine. The initial dose is 50–100 μg daily (50 μg for those >50 years and 25 μg in the elderly and those with cardiac disease). Increase the dose by 25 or 50 μg at intervals of at least 4 weeks.

Check the TSH each month and stop increasing the thyroxine dose when the TSH is normal. The usual maintenance dose of thyroxine is 100–200 μg daily. Treatment is usually lifelong. If the TSH is suppressed in young people, the thyroxine dose should be lowered in order to avoid osteoporosis.

Follow-up.

Once stable, TSH should be monitored annually.

Patients taking thyroxine replacement are exempt from prescription charges.

Quality and Outcomes Framework for Hypothyroidism

• Measure the TSH annually.

Administration

HYPERTHYROIDISM

Hyperthyroidism affects about 0.7% of the population.

Diagnosis

TFTs reveal a low TSH and a raised T4 or T3.

Management

Tip

Refer all patients to endocrinology. The aetiology must be determined and the commonest causes are Graves’ disease (80% of cases), toxic multinodular goitre and toxic adenoma.

While awaiting assessment, use propranolol 40 mg tds for rapid relief of symptoms if necessary, in conjunction with carbimazole.

Start carbimazole 15–40 mg daily and maintain the dose until the patient becomes euthyroid, usually after 4–8 weeks. Then reduce the dose progressively to a maintenance of 5–15 mg daily. Assess every 6 months with TFTs. Carbimazole can rarely induce agranulocytosis, which may present as e.g. a sore throat. A white blood cell count should be performed if there is any clinical evidence of infection.

Carbimazole treatment is usually continued for 12–18 months in the hope of inducing lifelong remission. On stopping treatment, check TFTs. Follow-up beyond 1 year is not necessary, but patients should be warned about the possible recurrence of symptoms.

Treatment with radioactive iodine may be recommended. Thereafter, TFTs should be monitored long-term, as most patients become hypothyroid at some stage, even many years after treatment.

THYROID ENLARGEMENT

A thyroid swelling can involve the whole gland (goitre) or consist of an isolated nodule.

Check TFTs.

All thyroid nodules should be referred to a thyroid surgeon, urgently, in order to exclude malignancy. A simple or multinodular goitre in a euthyroid patient need only be referred if it bothers the patient. This can be confirmed by arranging a thyroid ultrasound scan.

OBESITY

Obesity is defined in terms of body mass index (BMI) (see p. 152):

• 25–30, overweight (grade I)
• 30–40, moderate obesity (grade II)
• >40, severe obesity (grade III).

About 30% of the UK population have grade I obesity, 3% have grade II obesity and 0.3% have grade III obesity. Mortality rates double at a BMI of 35, and increase exponentially with increasing BMI. Obesity is often associated with psychosocial problems, and can exacerbate various medical problems, including:

• hypertension
• ischaemic heart disease
• diabetes mellitus
• respiratory problems
• arthritis
• gallstones
• varicose veins
• intertrigo.

Management

• In order to lose weight, energy output must exceed energy input.
• Discuss breaking the diet/weight-gain/diet cycle by encouraging normal eating patterns.
• Think in the long term. Set realistic goals and take things slowly.
• The patient might expect to lose 0.5–1.0 kg per week on a reduced-calorie diet of e.g. 1000 kcal per day.
• In general, avoid the use of drugs for treating obesity, as they tend to work only in the short term. However, consider:

– Orlistat 120 mg tds at mealtimes if the BMI is >30 or if the BMI is >28 in the presence of other risk factors, e.g. type 2 diabetes, hypertension, hypercholesterolaemia. It must be prescribed in the context of support, monitoring and counselling (see BNF guidelines).
– Sibutramine 10–15 mg daily. Similar guidance to orlistat license. BP must be checked regularly.

• Encourage regular exercise.
• Consider involving the practice nurse or hospital dietician. Outside agencies, e.g. Weight Watchers, can be very helpful.

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