Impaired glucose tolerance, diabetes mellitus, Hypothyroidism and Hypoparatiroidism
- Impaired glucose tolerance and diabetes mellitus (DM)
IMPAIRED GLUCOSE TOLERANCE (IGT)AND DIABETES MELLITUS (DM)
Glucose tolerance abnormalities and diabetes mellitus (DM) are common complications in patients with TM. Disturbances of glucose omeostasis range from increased insulin resistance and mild glucose intolerance to overt diabetes mellitus. Patients with mild disorders are usually asymptomatic; impaired glucose tolerance (IGT) is common, occurring in up to 24 %.The prevalence of DM and impaired glucose tolerance (IGT) in adolescents and young adults with TM conventionally treated with desferrioxamine varies in different series (up to 10.5% and 24%, in different series. The considerable variation in the occurrence of glycemic abnormalities can be partially explained by the marked differences in the age composition of cohorts, their genetic background, transfusion regimens, degree of chelation and the screening method used.
The initial insult appears to be due to iron-mediated insulin resistance rather than defective insulin production, but pancreatic β-cell damage and insulin deficiency subsequently develop as a result of direct toxic damage from iron deposition.
The interplay between liver siderosis, hepatitis C, zinc deficiency, autoimmunity, pancreatic fat content and patient's genotype may facilitates and accelerates the progression to DM (Figure).
Early recognition of glucose abnormalities is essential. OGTT should be done in every patient with TM after the age of ten or earlier if needed.
The most accurate method to evaluate altered glucose metabolism in patients with TM is still controversial. We recommend fasting blood glucose, insulin and calculation of homeostatic model assessment (HOMA-IR) index.Oral glucose tolerance test in subjects with high serum ferritin and/or chronic liver disease can identify patients at high risk of glucose dysregulation and has been recommended at 10, 12, 14, and 16 years of age and annually thereafter.The diagnosis of IGT and DM is currently made during a period of stable baseline health according to the American Diabetes Association (ADA) criteria.
|1. Insulin-dependent (IDDM, type I)||Typical symptoms: glycosuria, ketonuria; random plasma glucose (PG) > 200/mg/dl|
|2. Non-insulin-dependent (NIDDM, type II)||Fasting PG > 140 mg/dl on OGTT** more than once and in the absence of precipitating factors|
|Impaires Glucose Tolerance (IGT)||FPG < 140 mg/dl with 2 hour > 140 mg/dl on OGTT**|
* Details of this classification and its rationale can be found in National Diabetes Data Group: Classification and diagnosis of diabetes mellitus and other categories of glucose tolerance. Diabetes 1979; 28:1039.
* Oral glucose tolerance testing - 1.75 mg/kg body weight, to a maximum of 74 g.
• Intensive iron-chelation therapy and prevention and treatment of chronic hepatitis C are now the most important issues in managing impairment of glucose homeostasis in patients with transfusion dependent β-thalassemia.
• Management of DM should be individualised
• Healthy diet suitable for DM ( as assessed and advised by expert dietitian)
• Regular physical activity
• There is very limited published data on the efficacy and safety of oral antidiabetic agents in patients with TM. The only drugs used in smallstudies in this context with good effect were metformin, glibenclamide, sitagliptin or acarbose.
• When overt DM develops, patients require daily subcutaneous injections of insulin to normalise blood sugar levels.
• Diabetic patients with TM should regularly be seen by a specialized multidisciplinary team with expertise in both diabetes and TM, including ongoing diabetes self-management education. The team should include an endocrinologist and dietician with experience in TM.
• TM women with pre-existing diabetes should have pre-pregnancy counselling and planning to aim for optimal glycemic control before andthroughout pregnancy to minimize adverse pregnancy outcomes.
• Monitoring glycaemic control in thalassaemia patients is the same as with non-thalassemic patients with DM.
• Diabetic patients with TM should regularly be seen by a specialized multidisciplinary team with expertise in both diabetes and TM, includingongoing diabetes self-management and continuous education. The team should include an endocrinologist and dietician with experiencein TM.
• Self-glucose monitoring (SGM) at home using glucometers.
• Urine ketones if blood sugar >250mg/dl
• Fructosamine determination is useful for monitoring diabetes in these patients.
• Periodic assessment of renal function
• A microalbumin test is used to detect early signs of kidney damage in people who are at risk of developing kidney disease (once a year). If albumin in the urine (micro-albuminuria) is detected, it should be confirmed by retesting twice within a 3-6 month period.
• Evaluation of retinopathy
The reported thyroid dysfunction seen in patients with TM includes primary hypothyroidism-caused abnormalities of the thyroid gland, subclinical hypothyroidism (Table) as well as secondary hypothyroidism (CH).
The frequency of hypothyroidism shows a discrepancy depending on the region, quality of management, and treatment protocols. The reportedfrequency of thyroid dysfunctions ranges between 13% and 60% in different studies and occurs after 10 years of age regardless of difference in the rate of prevalence, largely as in the form of subclinical hypothyroidism.We have documented a prevalence of CH of 6% in patients with a chronological age below 21 years and 7.9% in those above 21 years (Figure).Clinicians should be alert for the diagnosis of CH through accurate interpretation of thyroid function tests.
Treatment depends upon the severity of organ failure (Figure). Good chelation therapy compliance may prevent or improve hypothyroidism (sub-clinical hypothyroidism - basal TSH 5 to 8 mUI/ml).Patients with mild or overt hypothyroidism should be given L-thyroxine, provided that the patient has normal cortisol levels.
In the general population, hypoparathyroidism (HPT) can be transient or permanent, inherited or acquired, or caused by inability of arathyroid gland to synthesize or secrete PTH. This may be due to abnormal development of the parathyroid gland, destruction of parathyroid tissue, or peripheral resistance to PTH.In adults, the most common cause of HPT is parathyroid gland injury or inadvertent removal during thyroid surgery whereas in patients withthalassemias it is mainly attributed to iron overload, secondary to multiple blood transfusions and suboptimal chelation therapy.
a) The diagnosis is based on low serum calcium, high phosphate and low PTH levels, in respect to serum calcium level.b) ECG to detect any abnormality in the electrical activity of the heart
HPT requires lifelong therapy with vitamin D or metabolites. Both under- and overtreatment can lead to unintended outcomes that can be irreversible.
In undertreated or late treated patients with HPT, where there is a combination of chronichypocalcemia and hyperphosphatemia, ectopic calcifications in organs may occur (Figure and Table). In over treated patient the risk of kidney stones and nephrocalcinosis is markedly increased.