Endocrine Abstracts (2005) 10 P19

Informed consent for thyroxine replacement?

DH Gannon & T Ulahannan

Gloucestershire Royal Hospital, Gloucester, United Kingdom.

A 45 year old female with Type 1 DM for 12 years presented with malaise and frequent episodes of hypoglycaemia. Thyroxine was titrated to 150 mcg once daily over 2 months because TSH was 94 mIU/L [0.2–5.50 mIU/L]. However, her malaise and hypoglycaemia deteriorated, she also developed dense hyperpigmentation in the skin.

Primary hypoadrenalism was confirmed by lack of response to 250 mcg IV Tetracosactide (Serum Cortisol at Time 0 min: 98 nmol/L; Time 30 min: 102 nmol/L). Hydrocortisone and Fludrocortisone were commenced. Her malaise, hypoglycaemia and hyperpigmentation subsided.

Elevated TSH can on rare occasions be the first presentation of Addison’s disease. Thyroxine replacement without hydrocortisone cover can prove fatal due to exacerbation of glucocorticoid deficiency. Recently, 9/814 (1.1%) of Type 1 DM subjects were positive for auto-antibodies to both the thyroid and adrenal glands, 227/814 (28%) had positive thyroid antibodies but no adrenal antibodies. Therefore 9/236 (3.8%) of Type 1 DM patients with thyroid autoimmunity would have adrenal antibodies. Addison’s disease presents before hypothyroidism in 50% of cases so 1.9% of Type 1 DM patients with thyroid autoimmunity may be at risk of adrenal failure if thyroxine was started without hydrocortisone cover.

Informed consent for treatment is a GMC attribute of good medical practice. Recent medico legal experience has shown that the courts would require that the medical practitioner disclose to the patient any material risk of an adverse event of over one percent. In this context, practitioners should inform patients of the possibility of adrenal insufficiency when starting thyroxine in patients with Type 1 DM and screen for Addison’s disease with a 9 am Cortisol measurement.

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