Endocrinology



Endocrinology






The ageing endocrine system


Ageing and thyroid function

Normal thyroid function is preserved in healthy older people. Median TSH levels drift upwards very slowly with age, but remain within normal limits in the absence of disease. Lower triiodothyronine (T3) and TSH levels seen in institutionalized older people and in very advanced old age (>95 years) are probably due to illness.


Sick euthyroid syndrome



  • TFTs are often abnormal in euthyroid patients who are ill with non-thyroid systemic disease; this reverses spontaneously when the underlying illness improves

▶Do not automatically initiate thyroid treatment changes



  • Changes depend on illness severity, and when TFTs are checked (during acute illness or recovery)


  • TSH secretion decreases early in the illness. Falls in levothyroxine (T4) and (especially) T3 may follow, the result of reduced TSH, lower thyroid hormone binding and reduced peripheral T4 → T3 conversion


  • Changes are more likely due to true hypothyroidism if:



    • Free T4 levels are low


    • Changes are severe


  • Secondary hypothyroidism (due to hypothalamo-pituitary failure) causes a similar pattern of TFTs, but is very much less common, and other features of pituitary failure are present (eg hypogonadism)


  • In the convalescent phase following illness, TSH may be elevated as low thyroid hormone levels drive TSH production. For a time, TSH may be high and T4/T3 low, mimicking primary hypothyroidism. TFTs repeated a few weeks later are usually normal.


Ageing and glucose metabolism

In older people:



  • Glucose-induced insulin release is delayed and reduced in size


  • Insulin-induced suppression of hepatic glucose production is delayed


  • Insulin-mediated peripheral (muscle and fat) glucose uptake is reduced

In addition to reductions in physical activity and lean muscle mass, the factors listed here lead to higher frequency of impaired glucose tolerance (IGT) with age. IGT is associated with macrovascular disease but not with specific diabetic complications. A minority of people with IGT progress to diabetes.




Diabetes mellitus

Diabetes is much more common with age: about 40% of new diagnoses are in people over 65. Prevalence in people over 65 is 10% in the UK, up to 50% in some ethnic groups and obese patients.


Comparing type 1 and type 2 diabetes



  • Both type 1 (insulin-dependent; IDDM) and type 2 (non-insulin dependent; NIDDM) diabetes can occur in older people. The prevalence of type 2 is much higher


  • In overweight older people, diabetes is mostly due to peripheral tissue insulin resistance (type 2). Glucose-induced insulin release is normal


  • Lean older people with diabetes often have impaired insulin release and may have islet cell antibodies more typical of type 1 diabetes. They respond poorly to oral hypoglycaemics


  • There are increasing numbers of older people with type 1 diabetes who developed the disease in early or mid-life and have survived decades on insulin, sometimes with no or few complications


  • Many people with type 2 diabetes progress to require insulin to achieve acceptable glycaemic control. This group is insulin-requiring (hence IRDM) and are unlikely to develop ketoacidosis if insulin is withdrawn


  • When assessing a patient on insulin, determine whether they are insulin-dependent (type 1; must always have background insulin infused) or insulin-requiring (type 2; in which insulin may safely be withheld for a time, without risk of ketosis)


Secondary diabetes

More common in older people. Causes include:



  • Drugs. Often steroids, sometimes high-dose thiazides, rarely other drugs


  • Pancreatic disease, eg chronic pancreatitis


  • Other endocrine diseases, eg Cushing’s, hyperthyroidism


Presentation



  • Diabetes often presents atypically or late in older people


  • Up to 50% of older people with diabetes are undiagnosed. This is at least partly due to physiological age-related changes, eg the renal threshold for glucose increases (glucosuria and polyuria occur later) and the thirst mechanism is impaired (polydipsia occurs later)


  • The diagnosis is often made by screening blood or urine tests, or during intercurrent illness


  • Think of diabetes in many clinical circumstances, eg coma, delirium, systemic stress (eg pneumonia), oral or vaginal thrush (candida), vulval itch (subclinical candida), cellulitis (and necrotising fasciitis), weight loss, urinary incontinence, polyuria, malaise, vascular disease or peripheral neuropathy


  • Steroid administration may reveal a diabetic tendency—always monitor, especially when high doses are used




HOW TO … Diagnose diabetes in older people



  • Confirm the diagnosis with a random blood sugar or fasting sugar. Criteria are the same as for younger patients


  • In general, the diagnosis is confirmed with a second measurement, unless the diagnosis is clear (eg severe hyperglycaemia with metabolic decompensation). A single high measurement in the absence of symptoms is not diagnostic


  • In some older diabetic people, fasting sugars may be normal. This is more common in lean older people, who have only postprandial hyperglycaemia. If in doubt, do an oral glucose tolerance test


  • Elevated glycosylated haemoglobin (HBA1c) levels are only moderately specific and sensitive to diabetes and are not sufficient either to confirm or to exclude the diagnosis. HBA1c is helpful in monitoring established disease


  • Screen annually in those with risk factors (eg family history, obesity), at least every 3 years in those without


Diagnostic criteria

At least one of the following criteria must apply:



  • Symptoms + random plasma glucose >11.1mmol


  • Fasting plasma glucose >7.0mmol


  • 2-hr plasma glucose >11.1mmol during oral glucose tolerance test (75g anhydrous glucose or the equivalent volume of a proprietary glucose drink such as Lucozade)


Obtaining a fasting blood sugar



  • Give the completed request card to the patient


  • The patient should make an early morning appointment with a phlebotomist or general practice nurse


  • There must be no caloric intake for at least 8hr before the blood test



    • Tell the patient to go for the blood test before breakfast


    • Clear fluids (water; tea or coffee without milk or sugar) may be taken


    • Other beverages or food must be avoided



Diabetes: treatment



  • In all patients, aim to avoid symptoms of hyper- and hypoglycaemia


  • In the more robust older patient, good glycaemic control probably reduces complication rates:



    • Aim for HBA1c levels close to normal (6.5-7.5%) and fasting sugar of 5-7mmol/L


  • The frail, and the very old (>80 years) have not been included in most prospective treatment studies. There is therefore doubt whether tight glycaemic control improves long-term outcome. Shorter-term benefits may include improved cognition, functional status, mood, and vitality



    • Balance the potential benefits of tight control with the risk of drug-induced symptomatic hypoglycaemia, falls, and fractures


    • Symptoms of hypoglycaemia may go unrecognized or be considered an ageing change by carers


    • Reasonable targets for the frail are HBA1c 7.5-8.5% and fasting sugar 7-10mmol/L


    • Vulnerable older patients are probably at higher risk of hypoglycaemia (eg causing confusion and falls) than hyperglycaemia. In some circumstances (eg where glucose levels appear very variable) it may be safest to accept very high ceiling levels (eg up to 20mmol/L)

▶In general, in frail older people, the approach is to reduce symptoms, not to normalize sugars.


Diet



  • Dietary change is often the only treatment needed in obese people with type 2 diabetes


  • Wholesale changes to diet may not be accepted, but even small changes are worthwhile and on their own can result in much increased insulin sensitivity within weeks


  • Full compliance may not be possible for the functionally or cognitively impaired, but an experienced dietician or nurse working with the patient and family is usually effective


  • Severe dietary restrictions are often not appropriate, especially for the very old or very frail


  • Beware the strict diet that takes enjoyment from (the last months of) life while giving little back


Education



  • Educate family, carers, and nursing home staff continually


  • Provide simple written information and instructions


  • The approach must be tailored to the individual, taking note of cognitive and sensory impairments


Other interventions



  • Exercise, especially endurance exercise (eg walking, cycling) improves insulin sensitivity


  • Weight loss. Even modest reductions are beneficial


  • Reduction of other vascular risk factors, including smoking


  • Home or pendant alarm systems in case of hypoglycaemia



Disease surveillance

Patients should be encouraged to take control of their own diabetic control and facilitated to monitor their own blood sugars. In addition they should be reviewed at least annually. In the very frail or dependent, regular reviews remain vital, eg to ensure that treatments remain appropriate and that adverse effects have not occurred.



  • Assess diet/drug concordance


  • Check weight


  • Optimize cardiovascular risk factors including blood pressure and lipids


  • Assess glycaemic control


  • Blood glucose testing, supplemented by 6-monthly HbA1c estimation is the preferred method


  • Urine glucose testing is less reliable, due to increased renal glucose threshold


  • Examine for evidence of complications, including microalbuminuria, an early sign of nephropathy


  • Ensure regular retinal screening is in place


  • Check feet and advise on their care (see image ‘The elderly foot’, p.490)

▶Utilize the advice and support of nursing staff with specialist knowledge of diabetes—either community nurses with a special interest, or dedicated diabetes specialist nurses.



Diabetes: oral drug treatment


Biguanides

For example: metformin (start at 500mg od)



  • Commonly used as first-line drug therapy in obese (BMI >25), elderly patients (where insulin resistance predominates)


  • Do not cause hypoglycaemia


  • Common side effects are nausea, diarrhoea, anorexia, and weight loss. These are less common if the drug is introduced slowly (500mg od, increased incrementally each week to maximum 850mg tds)


  • Can cause lactic acidosis in patients with hepatic or renal impairment, or where tissue hypoxia increases lactate production



    • Use cautiously in patients with kidney impairment (avoided if eGFR <30), hepatic impairment or heart failure (even if treated). Age itself is not a contraindication


    • Stop in acutely unwell patients (especially with sepsis, respiratory failure, heart failure, or MI)


    • Discontinue before anaesthesia or the administration of radiographic contrast media, restarting if/when renal function normalizes


Sulphonylureas

For example: gliclazide (start at 40mg od)



  • Commonly used as first-line drug therapy in lean elderly patients (where impairment in insulin release predominates)


  • Can cause hypoglycaemia. This is uncommon if short-acting agents (gliclazide, glipizide, tolbutamide) are used. Avoid long-acting drugs (chlorpropamide, glibenclamide) which can cause prolonged and damaging hypoglycaemia. In patients taking these (often for years without problems), consider a switch to shorter-acting drugs


  • Commonly cause weight gain


Thiazolidinediones

For example: pioglitazone (start with 30mg od)



  • Effective in older people; do not cause hypoglycaemia. May be used:



    • As monotherapy, if intolerant of sulphonylureas and biguanides


    • In combination with either a sulphonylurea or biguanide if control with that combination has been unsatisfactory


    • Increasingly used as part of triple therapy to avoid introducing insulin


  • LFTs must be monitored, initially 2-monthly. Stop if dysfunction occurs. Mild abnormalities at onset secondary to fatty liver are not a contraindication


  • Can be used in mild/moderate renal failure. Avoid in heart failure. Doubles risk of bone fracture in women


  • Pioglitazone has a more favourable cardiovascular risk profile



α-Glucosidase inhibitors

For example: acarbose (start with 25mg bd twice daily, taken with the first mouthful of food)



  • Only moderately effective (HbA1c reduction 0.5-1%), either as first-line or add-on therapy. Despite modest potency and side effects, they have a place, and may, eg, help delay or avoid the need for insulin


  • Gastrointestinal side effects (flatulence, bloating, diarrhoea) usually settle with time and are less severe if the dose begins low and is increased slowly


  • There are no severe side effects. Hypoglycaemia is never a problem



HOW TO … Manage older diabetic people in care homes

In care homes:



  • The prevalence of diabetes is very high


  • Individual diabetic patients are at great risk of complications


  • Hypoglycaemia and other medication side effects are frequent

To enhance quality of care:



  • Every resident should be screened for diabetes on admission to the home and each year thereafter. Blood sampling is far more sensitive than urinalysis


  • Every resident with diabetes should have an individual care plan including at least: diet, medications, glycaemic targets, and monitoring schedule. Monitoring should be varied in time (pre-/post-prandial; breakfast, lunch, evening meal, late evening), to provide a more complete picture of glycaemic control


  • Diabetic diets should be available


  • An annual diabetes review should be performed by either a nurse with specialist training in diabetes, a GP, or a specialist (geriatrician or diabetologist)


  • An annual ophthalmic screening assessment should be performed. Rarely, domiciliary screening is available. Usually, the resident will need to leave the home to attend a specialist screening centre, but this is usually worthwhile as vision contributes significantly to quality of life


  • There should be easy access to specialist services including podiatry, optometry, diabetic foot clinic, dietetics, and diabetes specialist nursing


  • Each home with diabetic residents should have a diabetes care policy. Staff should have received training in the identification and treatment of diabetic emergencies and the prevention of complications



Further reading


Diabetes UK (2010). Good Clinical Practice Guidelines for Care Home Residents with Diabetes. London: Diabetes UK.



Diabetes: insulin treatment



  • Insulin is essential for the treatment of type 1 diabetes


  • Insulin is started in type 2 diabetes when oral agents fail to achieve adequate control, if hyperglycaemia is severe (especially if the patient is lean, and insulin deficiency likely), if a patient is unwell, and if oral drugs are contraindicated (eg hepatorenal impairment)


  • Side effects include:



    • Weight gain. Common. Lessened if an oral drug (especially metformin) is co-prescribed


    • Hypoglycaemia. Much more common with insulin than with any oral agent


Insulin regimens



  • Increasingly initiate treatment with very long-acting insulins (insulin glargine and insulin detemir) which are effective if given just once daily. These are particularly helpful in those who:



    • Require assistance (relative, nurse) with injections


    • Are frequently hypoglycaemic on other regimens, especially at night


    • Would otherwise need twice-daily insulin injections plus oral drugs


  • Alternative strategies, eg twice-daily insulin injections with pre-mixed insulins (eg Humalog® Mix 25) are becoming ‘old-fashioned’. They are rarely initiated now but some older patients have been stable for years on such treatment so there is no advantage in changing


  • Daily long-acting insulin once daily can be supplemented by oral hypoglycaemics during the day


  • If eating is very erratic, consider giving short-acting insulin after each meal based on what has been eaten—a simple sliding scale


  • Regimens based on rapid-acting insulin alone or a basal-bolus structure (the mainstay of management in younger patients with type 1 diabetes; provide an insulin profile as close to health as possible), are rarely appropriate in older people unless lifestyle (meals and activity) are especially chaotic and the patient has the cognitive and physical ability to manage dosing


Initiating insulin



  • Involve the MDT (especially the diabetic nurse specialist)


  • If the patient is likely to need professional support to administer insulin, then also involve community teams—insulin administration may be very time-consuming for them


  • Patients may be very reluctant to begin, because of fears about injections, hypos, or learning new skills


  • Remember insulin administration issues: cognition, dexterity, and vision


  • Pre-mixed insulins avoid having to draw up multiple types of insulin


  • Insulin pens make the measuring of doses much easier for patients, but syringes are more suitable when insulin is drawn up by a third party (relative or nurse)


  • In disposable pens, the vial is pre-loaded. This is helpful for patients who are not so dexterous



  • Some patients are able to self-inject, but cannot safely draw up insulin into syringes or use an insulin pen. In this case, doses may be drawn up in syringes by relatives or the community nurse, and stored in a refrigerator until needed


  • If insulin is given by a relative, what happens during family holidays?


Changing insulin requirements



  • Always consider whether your patient is on the correct insulin regimen (type and dose)


  • Earlier in the course of the disease, insulin requirements often rise as disease severity increases


  • In advanced old age, insulin requirements often fall as appetite declines, body weight drops, and renal function deteriorates. Type 2 diabetic patients on insulin may get off insulin altogether. Stop insulin, maximize oral drug treatment, and monitor regularly


  • Dying patients can often have treatment withdrawn (see image ‘HOW TO … Manage diabetes in the terminally ill patient’, p.434)



Further reading


European Diabetes Working Party for Older People. Clinical guidelines for type 2 diabetes mellitus. online: image http://www.eugms.org/index.php?pid=30.



Diabetes: complications

In general, these are more common in older people, especially vascular complications. Evidence for risk reduction in very old diabetic patients is weak. In practice, evidence from younger age groups is extrapolated to apply to older groups, except in the very frail and/or those with very poor life expectancy, where a more conservative approach may be appropriate. Make an individual decision.


Vascular

A very common cause of morbidity and mortality. The risk of MI is as high in diabetic patients without known coronary disease as it is in non-diabetic patients who have had an infarct.



  • Improve glycaemic control to the extent that it is possible without inducing hypoglycaemia


  • Treat hypertension if it is persistent despite lifestyle management:



    • Target blood pressure <140/<80mm Hg; lower if eye or kidney disease


    • In the frail, target blood pressure <150/<90mm Hg


    • The drug class used is less important than the reduction in blood pressure achieved. β-blockers are not contraindicated. ACE inhibitors and ARBs may have an important additional effect in preventing nephropathy


  • Treat hyperlipidaemia except in the very elderly and frail. Statins are well tolerated. The Heart Protection Study demonstrated benefit in diabetic patients with cholesterol >3.5mmol


  • Stop smoking. Health benefits begin in 3-6 months


  • Low-dose aspirin should be offered to all older patients with diabetes (since 10-year coronary risk is >15%) unless there is a contraindication. Control hypertension beforehand

▶In older people, blood pressure control is as important as glycaemic control in reducing cardiovascular risk.


Neuropathy

This is more common in older diabetic people and is often asymptomatic although may contribute to falls (see image ‘Balance and dysequilibrium’, p.112). Annual screening is necessary: check pinprick, vibration sense, light touch (nylon monofilament), and reflexes.



  • Classically and most commonly a distal symmetrical polyneuropathy is seen. Consider other causes


  • Mononeuropathy is usually of sudden onset, asymmetrical and resolves over weeks or months. Often painful. May coexist with polyneuropathy. For example:



    • Third nerve palsy. Most common. Causes ophthalmoplegia


    • Diabetic amyotrophy. Pelvic girdle and thigh muscle weakness and wasting. Difficulty rising from chair


  • Diabetic neuropathic cachexia. Painful peripheral neuropathy, depression, anorexia and weight loss

Treatment is to exclude other causes, to optimize glycaemic control, to control pain, and to support the patient through the illness, treating complications (eg depression) as they arise.



Nephropathy

A major problem in older diabetic people.



  • Microalbuminuria indicates a group at high risk of progression. Treat hypertension aggressively (preferentially with ACE inhibitors or ARBs), target BP 130/80 and optimize glycaemic control


  • If renal function deteriorates rapidly, exclude papillary necrosis by obtaining emergency renal tract ultrasound


Eyes

Retinopathy, glaucoma, and cataract are common (see image ‘The eye and systemic disease’, p.579). All diabetic people should have annual screening ophthalmic assessment that includes retinal examination (fundoscopy via a dilated pupil) and visual acuity testing. This is usually provided by ophthalmic specialist clinics or by diabetologists (or other physicians) with particular expertise. Indications for urgent referral for specialist assessment include:



  • Inadequacy of fundoscopic examination, eg due to cataract


  • Diabetic maculopathy. Either exudates close (<1 optic disc diameter) to the macula, or suspicion of macular oedema (nothing may be observed that is abnormal, but visual acuity is impaired)


  • Preproliferative changes (many cotton wool spots, flame or blot haemorrhages, venous change (beading, loops))


  • Proliferative changes (pre-retinal or vitreous haemorrhage new vessels, retinal detachment)

▶Preventing blindness depends on early diagnosis of diabetes, good glycaemic control, effective retinal screening, and early treatment of maculopathy and retinopathy.


Ears

Malignant otitis externa, manifesting as severe ear pain, is more common in diabetes (see image ‘Osteomyelitis’, p.488).


Teeth

Gum disease and caries are more common. Good oral hygiene and regular dental assessment are essential.


Feet

Neuropathy and vascular disease lead to infection, injury, and ischaemia. Outcomes include pain, ulceration, immobility, and amputation. Impeccable foot care is essential (see image ‘The elderly foot’, p.490).



Diabetic emergencies

Although overall presentations with diabetic emergencies are diminishing, two are especially important—hypoglycaemia and hyperosmolar non-ketotic state (HONK). However, older patients can present with any diabetic problem, including diabetic ketoacidosis.


Hyperosmolar non-ketotic state

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Jul 22, 2016 | Posted by in GERIATRICS | Comments Off on Endocrinology

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