Page 442 - Medicine and Surgery

P1: FAW
BLUK007-11 BLUK007-Kendall May 25, 2005 8:5 Char Count= 0

438 Chapter 11: Endocrine system

1. Sodium retention and hence water retention ↑ Plasma volume
2. Inotropic effects on heart ↑ Cardiac output
3. ↓ K + (hypokalaemia causes smooth muscle contraction) Vasoconstriction +
= Hypertension

Figure 11.9 Effects of aldosterone.

1. ↑ Hepatic gluconeogenesis and glycogen synthesis Hyperglycaemia
2. ↓ Peripheral glucose uptake by muscle and fat cells
3. ↑ Free fatty acid release by lipolysis in adipose tissue
4. ↑ Peripheral catabolism and release of amino acids Muscle wasting
5. Inhibition of fibroblasts, causing reduced amounts of collagen Thinned skin, striae
6. ↓ bone formation and ↑ bone resorption Osteoporosis
7. Immunologic effects, mainly ↓ inflammation and ↑ migration of ↑ Susceptibility to
inflammatory cells to areas of injury infections
8. ↓ Sodium and water excretion
9. ↓ Calcium absorption and ↑ calcium excretion
10. Influences behaviour, cognitive function and neuronal development
Figure 11.10 Effects of cortisol.

are most important during fasting, illness or surgery (see Aetiology
Fig. 11.10). The excess of glucocorticoid may be endogenous or ex-
ogenous. Endogenous glucocorticoids may result from
high ACTH causing excessive adrenal stimulation or
Androgens
may result from a primary adrenal disease in which case
Androstenedione is produced by the adrenal cortex and
ACTH levels will be low (see Table 11.10).
is converted to testosterone and dihydrotesterone. In
males, 95% of active testosterone is derived from the
testis, so adrenal androgen excess or deficiency is rel- Pathophysiology
atively insignificant. In females 50% of the peripheral Cortisol opposes insulin, with a catabolic effect. Adrenal
production of testosterone is from adrenal androgens. mineralocorticoid secretion is mildly raised, but the
Female neonates with congenital adrenal hyperplasia glucocorticoids also have some mineralocorticoid effect.
have ambiguous genitalia (clitoromegaly). Adults with Excess androgens can cause mild hirsutism, menstrual
Cushing’s syndrome and adrenal tumours with hyper- irregularities in women, and can inhibit LH and testos-
secretion of adrenal androgens have acne, hirsutism and terone secretion in men, reducing libido.
virilisation.
Clinical features
Common features include centripetal obesity (moon
Cushing’s syndrome
face, buffalo hump), plethora, osteoporosis, proximal
Definition myopathy, easy bruising, striae, acne, hirsutism, poor
Cushing’s syndrome is the clinical syndrome resulting wound healing and glucose intolerance. Gonadal dys-
from excess circulating glucocorticoids. function leads to oligo- or amenorrhoea or impotence.