Pituitary functional testing

The most serious adverse effect of protirelin is pituitary apoplexy (pituitary hemorrhage or infarction, characterized by severe headache, visual loss, and often by pituitary failure, hypotension, and coma). This complication has been described in 15 cases after pituitary function testing... 

Masago A, Ueda Y, Kanai H, Nagai H, Umemura S. Pituitary apoplexy after pituitary function test a report of two cases and review of the literature. Surg Neurol 1995 43(2) 158-64. 

The changes in base-line hormone secretion are useful for interpretation of drug effects, it is often advisable to include dynamic function tests based on stimulation of pituitary hormone secretion, or of gonadal and adrenal hormone secretion. Examples for pituitary testing have been mentioned above and secretion. Typical pituitary function tests are the TRH test for TSH secretion, the LHRH test for secretion of FSH and LH, and the mono iodo-tyrosine (MIT) test for prolactin secretion. Synthetic CRF may be injected to stimulate secretion of corticotropin (ACTH), more frequently the injection of corticotropin is used to stimulate the adrenal directly. At the target organ level, similar... 

When puberty is delayed in a girl, measurement of serum gonadotropins is useful for diagnostic purposes. Low concentrations may indicate pituitary failure, whereas concentrations elevated mto the postmenopausal interval mdicate definite gonadal failure. In the latter case, chromosome studies are indicated. In the former case, pituitary function testing and radiography may be helpful. Patients... 

In view of this man s marked increase in prolactin, which does not change significantly during the combined anterior pituitary function test, one can make a diagnosis of prolactinoma. 

Combined anterior pituitary function test (CAPFT)... 

The clinical biochemistry laboratory is commonly called upon to establish if there is excessive hormone secretion. Simple screening test.s to eliminate other diagnoses are followed by more complicated dynamic tests. If a pituitary tumour is suspected, it is important to establish the extent of damage to other pituitary functions. The combined anterior pituitary function test (Fig. 3) is used here. TRH. GnRH and insulin are given from separate. syringes. All hormones are measured at 0, 30 and 60 min, and cortisol and GH additionally at... 

When investigating any pituitary tumour it is important to a.ssess if there is disruption of other pituitary hormone secretion by means of aconibined anterior pituitary function test (p. 77). 

Oral contraceptives have their most significant effect on endocrine parameters. Blood cortisol, thyroxine, protein-bound iodine, T3 uptake, and urinary free cortisol are elevated. Urinary 17,21-dihydroxy steroids, 17-ketosteroids, and estrogens are decreased. There is no effect on urinary catecholamines or VMA (Table 10) (LIO). The effect of thyroid functions tests is due to the administered hormone stimulating an increase in the production of thyroid-binding globulin which in turn binds 1-thyroxine. The lowering of free thyroxine stimulates the anterior pituitary to produce thyrotropin, which in turn stimulates the thyroid to produce more thyroxine. Since the additional thyroxine is bound to the extra protein, there is an equilibrium and the patient remains clinically euthyroid, but the protein-bound iodine and the thyroxine are elevated. 

Castracane VD, Allen-Rowlands CF, Hamilton MG, et al. 1982. The effect of polychlorinated biphenyl (PBB) on testes, adrenal, and pituitary function in the rat. Proc Soc Exp Biol Med 169 343-347. 

Thyroid function tests are often altered by somatropin because of increased conversion of T4 to T3, but this is clinically insignificant at low doses (SEDA-21, 453). One child with Prader-Willi syndrome had a fall in serum thyroxine concentration during somatropin therapy and needed thyroxine replacement (33). Hypothyroidism developed in 11 of 46 growth hormone-deficient children treated with somatropin (34). Prior abnormalities in hypothalamic-pituitary function and alterations in thyroid hormone metabolism, probably both, contributed to the high incidence of hypothyroidism, which was similar to that in previous studies. 

Thyroid disorders may be divided into over- and underproduction of the thyroid hormones. These may be caused by thyroid gland disorders or disorders of the pituitary gland (TSH production) or hypothalamus (thyrotropin-releasing hormone release). Thyroid hormone deficiency in infancy may cause mental retardation if it is not corrected immediately after birth. For this reason, many states require thyroid function tests in all newborns. In adults, thyroid deficiency may be caused by Hashimoto s thyroiditis, an immune disorder, or dietary iodine deficiency, in which case it is called simple goiter. The term "myxedema" has been used to refer to hypothyroidism of whatever cause. Myxedemas may... 

In this method, the repeated dose administration with a design similar to toxicology studies is preferred. Studies of up to four weeks duration need to include function tests for hormone secretion (basal concentrations, stimulation or inhibition), and for hormone contents of endocrine organs and tissues (e.g. hypothalamus, pituitary gland, reproductive organs). In the Endocrine Survey, 5 to 7 days of treatment are mandatory because adaptation and response of hormone-dependent organs to the treatment requires that a steady state be reached. Repeated-dose treatment with at least two doses is also needed for a sufficient... 

In order to assess pituitary function, inclusion of the LHRH stimulation test for LH and FSH is recommended in male rats and female rats, and the mono-iodo-tyrosin (MIT) stimulation test for prolactin secretion is recommend at least for the female animals. Pituitary content of LH, FSH and prolactin should always be determined at autopsy (half of the pituitary for hormone assays and the other half for histology). 

Insulin-induced hypoglycaemia can also be used as a test of anterior pituitary function (growth hormone and corticotropin are released). 

When assays for PRL became routinely available in the early 1970s, it became apparent that patients with elevations in PRL were observed more frequently than previously thought in clinical practice. However, PRL deficiency does not appear to have clinical significance except as an additional test of pituitary function in patients already known to have pituitary disease. 

Evaluation of endocrine function is an important part of the management of patients with pituitary tumors. Detection of hormone deficiencies before and after treatment and recognition of hormone-producing tumors are the two objectives of testing of pituitary function in patients with pituitary tumors. ... 

The assessment of anterior and posterior pituitary lobe function in patients with pituitary tumors is important in the identification of clinically significant hormone deficiency states caused by the tumor itself and for the reevaluation of patients after pituitary surgery or irradiation to detect hormone deficiencies that occur as a result of invasive treatment. Testing of pituitary function is usually performed under basal conditions but can be performed under provocative conditions to bring out subtle or mild deficiencies that are observed with disorders of the adrenal gland, thyroid, or gonads. Evaluation of pituitary reserve for GH or PRL is usually unnecessary in adult patients because deficiencies of these hormones are not believed to be clinically important. 

The lowered detection limits of the newer two-site immunoassays for the measurement of pituitary hormones now make it possible to distinguish an abnormally low value from the lower end of the normal reference interval. Although assessment of a particular aspect of pituitary function should also include clinical signs and symptoms of hormone deficiency and the measurement of hormones secreted by the pertinent endocrine gland (e.g., T4, cortisol, and testosterone), the newer, ultrasensitive assays for TSH, FSH, LH, and ACTH allow for an accurate distinction of a true low result from low normal. A scheme for testing of pituitary reserve is fisted in Box 50-6. 

Pituitary Eunction The Adrenal Cortex The Thyroid Pathophysiology and Thyroid Function Testing... 

For the reasons discussed previously (Section 7.3.5.I.), radioimmunoassays are unlikely to be any more useful than hemagglutination-inhibition tests for work in which the identity of the hormone in question is important. There is no reason to expect that indices of discrimination between radioimmunoassays and bioassays will be any better than those between hemagglutination-inhibition tests and bioassays. However, radioimmunoassays for FSH and LH are extremely sensitive, and can probably provide a satisfactory indication of pituitary function in health and disease. For this reason, it is virtually certain that such procedures will be employed on an ever increasing scale in the management of patients. 

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