439 If screening is undertaken, the test of choice is a sTSH. When coupled with FT4, the vast majority of clinically significant hyperthyroidism and hypothyroidism can be diagnosed. If symptoms are present or there are overt signs of disease, the initial testing should include sTSH, FT4, and FT3. Thyroid panels providing T4, T3, T7, FT4 index, and T3 uptake are no longer advocated. 440 441 442 ## KEY TREATMENT 443 444 Thyrotoxicosis is treated initially with β-blockers and antithyroid medication to control symptoms and stop synthesis and release of thyroid hormone into the periph-eral circulation (Bahn et al., 2011; Oiknine et al., 2006; Trivalle et al., 1996) (SOR: A). 445 446 Hypothyroid (TSH >10 mIU/L) replacement T4 dose is approximately 1.6 μg/kg/day (Oiknine et al., 2006) (SOR: A). 447 448 With the exception of thyroid antibody-positive subclinical hypothyroidism with TSH less than 10 mIU/L, prophylactic treatment has not been shown to have a positive effect on lipids or CAD risk (Bahn et al., 2011; Garber et al., 2012; Helfand, 2004; Ladenson et al., 2000) (SOR: A). 449 450 Treatment of subclinical hyperthyroidism should be considered when TSH is less than 0.1 mU/L in all patients older than 65 years and in patients younger than 65 years with any of the following comorbidities: heart disease, osteoporosis, menopause, or hyperthyroid symp-toms (ATA and AACE, 2011) (SOR: B). 451 452 453 ## Adrenal Glands 454 455 456 ## PHYSIOLOGY 457 458 The adrenal glands are located at the superomedial aspects of the kidneys. The glands consist of two endocrine tissues of different embryologic origins: the primarily steroid-producing adrenocortical tissue in the cortex and the catecholamine-producing chromaffin cells in the medulla. The adrenal cortex consists of three zones that vary in both their morphologic features and the hormones they produce. The outer, zona glomerulosa, is the unique source of the mineralocorticoid aldosterone. The intermediate, zona fas-iculate, and the inner, zona reticularis, produce the gluco-corticoids cortisol and corticosterone and the androgens dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S). The chromaffin cells in the adrenal medulla mainly secrete the catecholamines epinephrine and norepinephrine (Table 35-10) (Williams and Dluhy, 2008). 459 460 Mineralocorticoids are major regulators of extracellular fluid volume and potassium metabolism. Volume is regulated through a direct effect on the collecting duct of the kidney, where aldosterone causes an increase in sodium retention and in potassium excretion. The release of aldosterone is regulated by the RAS, plasma potassium levels, and ACTH. The RAS maintains the circulating blood volume by regulating aldosterone secretion. Aldosterone-induced sodium retention occurs in volume deficiency states, but aldosterone-dependent sodium retention is reduced when volume is ample. An increase in plasma potassium or a decrease in plasma sodium stimulates aldosterone release. ACTH stimulates mineralocorticoid output, but this effect on aldosterone secretion is transient. 461 462 *Table 35-10 Adrenal Gland Anatomy and Steroids* 463 464 465 < [... Output truncated due to length. 3836 tokens/14856 characters removed ...]

Cortex	Zona glomerulosa
	Aldosterone
	Zona fasciculata
	Zona reticularis
	Glucocorticoids
	Cortisol
	Corticosterone
	Dehydroepiandrosterone (DHEA)