Thyroid Hormone, Oestrogen, and Glucocorticoid Effects on Two Different Pituitary Glycoprotein Hormone Alpha Subunit Pools

Kourides, Ione A.; Weintraub, Bruce D.; Ré, Richard N.; Ridgway, E. Chester; Maloof, Farahe

doi:10.1111/j.1365-2265.1978.tb01511.x

Cited by 33 publications

(12 citation statements)

References 28 publications

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“…It has been postulated that the normal pituitary gland contains two functionally different pools of a-subunit, one synthesized by thyrotroph cells and the other by gonadotroph cells (Kourides et al 1978). In this study we found that iv TRH and LRH caused increases of serum a-subunit in con¬ trols.…”

Section: Discussionmentioning

confidence: 75%

Glycoprotein hormone α-subunit secretion in patients with pituitary adenomas: influence of TRH, LRH and bromocriptine

MacFarlane

Beardwell

Shalet

et al. 1982

Acta Endocrinologica

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Twelve patients with pituitary adenomas and increased serum concentration of the glycoprotein hormone \g=a\-subunitwere studied. Eight patients were acromegalic and one had a FSH1 producing tumour. The adenomas in 9 patients had undergone subtotal operative removal and/or external irradiation but no patient was studied within 3 months of these treatments.Many of the acromegalic patients, with moderately elevated \g=a\-levels,showed marked increases in \g=a\-concentration after TRH and/or LRH, compared with controls. The non-acromegalic patients, with the highest \g=a\-levels, showed poor responses to releasing hormones. These results suggest that excessive \g=a\-subunitsecretion in acromegalic patients is often under hypothalamic control whereas in non-acromegalic patients it is often autonomous.Seven patients, 4 with acromegaly, were then given oral bromocriptine, 5 mg over 3 h. There was a significant fall in log mean \g=a\-levelat 4 and 5 h (P < 0.02). Six patients took bromocriptine for 1\p=n-\2months. Log mean \g=a\-concentration was significantly reduced at the end of treatment (P < 0.02) and then recovered to basal levels after stopping treatment for one week. \g=a\-Subunit hypersecretion in some patients with pituitary adenomas is therefore modulated by dopaminergic control mechanisms.

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Section: Discussionmentioning

confidence: 75%

Glycoprotein hormone α-subunit secretion in patients with pituitary adenomas: influence of TRH, LRH and bromocriptine

MacFarlane

Beardwell

Shalet

et al. 1982

Acta Endocrinologica

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“…It is likely that the secretion of FAS by thyrotroph cells of our patients is lower than that of controls, and this dissocia tion from the behavior of TSH is in favor of pituitary damage. It is well known that FAS is not only secreted by the gonadotroph but also by the thyrotroph cells [3], In fact there is experimental evidence that FAS secretion in normal subjects is not completely under GnRH control [4] and that administration of a GnRH antagonist has only a partial suppressive effect on FAS levels [7], The poor response of FAS, both to LH-RH and to TRH stimu lation, indicates that the pituitary damage in the course of the disease concerns not only the gonadotroph but also the thyrotroph cells which are both sensitive to iron overload. It is interesting to note that the patients who responded better to LH-RH stimulation, also responded better to TRH stimulation and a significant correlation existed 216 Tato/Lahlou/Zamboni/De Sanctis/De Luca/ Free Alpha-Subunits in Beta-Thalassemia Arrigo/Antoniazzi/Roger between the response of FAS to LH-RH and TRH in those patients.…”

Section: Discussionmentioning

confidence: 99%

“…In the pituitary gland there are two separate a-subunit pools stimulated by hypotha lamic peptides: one arising from gonadotroph and stimu lated by LH-releasing hormone (LH-RH) and one from thyrotroph stimulated by thyrotropin-releasing hormone (TRH) [3]. The a-subunit is secreted by the anterior pitu itary also in a free form (FAS) [4,5].…”

Section: Introductionmentioning

confidence: 99%

Impaired Response of Free Alpha-Subunits after Luteinizing Hormone-Releasing Hormone and Thyrotropin-Releasing Hormone Stimulations in Beta-Thalassemia Major

et al. 1993

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In order to clarify whether the damage in gonadotropin secretion due to iron overload in patients with β-thalassemia is of pituitary or hypothalamic origin, 14 euthyroid patients (8 females and 6 males, age 15-24 years) affected by β-thalassemia major with hypogonadotropic hypogonadism were studied. Luteinizing-hormone (LH), follicle-stimulating hormone (FSH) and free α-subunit (FAS) were measured during LH-releasing hormone (LH-RH) stimulation test, and thyroid-stimulating hormone (TSH), prolactin (PRL) and FAS during thyrotropin-releasing hormone (TRH) stimulation test. During LH-RH stimulation, the mean basal LH, FSH and FAS levels were similar to those found in normal prepubertal children, but the peak values were lower than those found in such children. Also during TRH stimulation, the mean peak values of FAS were lower than those of normal prepubertal children, but the TSH response was normal. The lack of response of gonadotropins and FAS to LH-RH cannot exclude hypothalamic failure; however, the normal response of TSH to TRH, in spite of the poor response of FAS, indicates that the origin of hypogonadotropic hypogonadism is the pituitary damage concerning not only the gonadotroph but also the thyrotroph cells.

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“…The a-subunit is secreted in a pulsatile manner by the thyrotropes and by the gonadotropes (6), but especially by the latter (7). Its production is stimulated by TRH (7) and by GnRH (8) and is suppressed with the use of thyroid hormone (9) or estradiol (1,10) in the absence of nonfunctioning tumors. Regulation by GnRH is the most important one, with 90% concordance between the pulses of the a-subunit and of LH (11).…”

Section: Introductionmentioning

confidence: 99%

“…The a-subunit of glycoprotein hormones, usually detected in the serum of normal individuals (1)(2)(3), has been used as a tumor marker for gonadotropin-or TSH-secreting pituitary adenomas (4), for GH-secreting tumors (4,5) and for nonsecreting pituitary tumors (3,4). The a-subunit is secreted in a pulsatile manner by the thyrotropes and by the gonadotropes (6), but especially by the latter (7).…”

Section: Introductionmentioning

confidence: 99%

Pituitary glycoprotein hormone <FONT FACE=Symbol>a</font>-subunit secretion by cirrhotic patients

Oliveira¹,

Pizarro²,

Cassal

et al. 1999

Braz J Med Biol Res

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Secretion of the a-subunit of pituitary glycoprotein hormones usually follows the secretion of intact gonadotropins and is increased in gonadal failure and decreased in isolated gonadotropin deficiency.The aim of the present study was to determine the levels of the asubunit in the serum of patients with cirrhosis of the liver and to compare the results obtained for eugonadal cirrhotic patients with those obtained for cirrhotic patients with hypogonadotropic hypogonadism. Forty-seven of 63 patients with cirrhosis (74.6%) presented hypogonadism (which was central in 45 cases and primary in 2), 7 were eugonadal, and 9 women were in normal menopause. The serum a-subunit was measured by the fluorimetric method using monoclonal antibodies. Cross-reactivity with LH, TSH, FSH and hCG was 6.5, 1.2, 4.3 and 1.1%, respectively, with an intra-assay coefficient of variation (CV) of less than 5% and an interassay CV of 5%, and sensitivity limit of 4 ng/l. The serum a-subunit concentration ranged from 36 to 6253 ng/l, with a median of 273 ng/l. The median was 251 ng/l for patients with central hypogonadism and 198 ng/l for eugonadal patients. The correlation between the a-subunit and basal LH levels was significant both in the total sample (r = 0.48, P<0.01) and in the cirrhotic patients with central hypogonadism (r = 0.33, P = 0.02). Among men with central hypogonadism there was a negative correlation between a-subunit levels and total testosterone levels (r = -0.54, P<0.01) as well as free testosterone levels (r = -0.53, P<0.01). In conclusion, although the a-subunit levels are correlated with LH levels, at present they cannot be used as markers for hypogonadism in patients with cirrhosis of the liver.

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Thyroid Hormone, Oestrogen, and Glucocorticoid Effects on Two Different Pituitary Glycoprotein Hormone Alpha Subunit Pools

Cited by 33 publications

References 28 publications

Glycoprotein hormone α-subunit secretion in patients with pituitary adenomas: influence of TRH, LRH and bromocriptine

Glycoprotein hormone α-subunit secretion in patients with pituitary adenomas: influence of TRH, LRH and bromocriptine

Impaired Response of Free Alpha-Subunits after Luteinizing Hormone-Releasing Hormone and Thyrotropin-Releasing Hormone Stimulations in Beta-Thalassemia Major

Pituitary glycoprotein hormone <FONT FACE=Symbol>a</font>-subunit secretion by cirrhotic patients

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