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454 Chapter 11: Endocrine system

Pancreatic disease:At least two thirds of the pan- Insulin-resistant diabetes with acanthosis nigricans
creas must be lost to cause a type 1 diabetes like i. Young women who have polycystic ovaries and re-
syndrome. Causes include chronic pancreatitis, post- duced numbers of insulin receptors due to muta-
pancreatectomy, pancreatic cancer, cystic fibrosis or tions in the allele for the receptor gene.
haemochromatosis. ii. Older patients with antibodies to insulin receptors
Insulin counter-regulatory hormones inhibit insulin reducing their affinity for insulin.
secretion or cause insulin resistance. This includes drugs
and results in a type 2 diabetes like syndrome. Insulin therapy
Growth hormone (acromegaly)

Glucocorticoids (Cushing’s syndrome or disease, ia- Synthetic insulin is administered subcutaneously in

trogenic) avariety of regimens. Various insulins have been
Glucagon (glucagonoma) ‘designed’ with different pharmacokinetic effects (see

Catecholamines (phaeochromocytoma) Table 11.17).

Somatostatin (pancreatic somatostatinoma) Twocommon regimens are used (see Fig. 11.15):

Oral contraceptives and pregnancy probably due to Atwice daily adminstration of biphasic insulin, with

the oestrogens (and also increased cortisol seen in two thirds of the total daily dose given before breakfast
pregnancy). and one third given before the evening meal.
Drugs may inhibit insulin secretion or cause damage to Abolus of short or immediate acting insulin given
the pancreatic islets. three times a day at meal times and a medium or
Thiazides and phenytoin inhibit insulin secretion. long-acting insulin given at night. The advantage of

Pentamidine damages the β-cells. this regimen is that meal times and quantities can be

Insulin receptor defects.These are rare disorders and varied. If immediate acting insulin is used it is taken
include: at or immediately after the meal, if short acting is
DIDMOAD (diabetes insipidus, diabetes mellitus, op- used then this is administered 30 minutes before the

tic atrophy and deafness) meal.
Table 11.17 Insulin regimens

Type of Insulin No. of injections
(length of action) per day (usual) Description Name
Immediate 2or3 (plus once daily Lispro
Onset medium or long acting) Novorapid
Immediate
Duration 4 h
Short 2–4 (plus once daily medium Soluble Actrapid
Onset 0.5 h or long acting) Velosulin
Peak 2–4 h Humulin S
Duration 4–6 h
Medium 2 Isophane (insulin zinc and protamine Insulatard
Onset 3 h (a protein) suspension) Protaphane
Peak 6–10 h Insulin detemir (soluble insulin analogue) Humulin I
Duration 12–24 h Levemir
Long 1 Insulin zinc suspension (protein and zinc Human ultratard
Onset 3–4 h crystals) Lantus
Peak 12–18 h Insulin glargine (forms slowly absorbed
Duration ∼24 h subcutaneous crystals)
Biphasic 1–2 Mixture of soluble and isophane Human mixtard
Onset 0.5 h Humulin M5
Peak 2–10 h
Duration 12–18 h