Biphasic thyrotropin suppression in euthyroid and hypothyroid rats

Martin I. Surks, B. M. Lifschitz

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

To determine whether thyrotropin (TSH) suppression was characterized by a rapid and slow component in euthyroid rats, TSH concentrations were measured in concentrates of plasma pooled from groups of 8 euthyroid rats 24 hr after injection of a single dose of triiodothyronine (T3). Plasma TSH decreased after T3 injection to values 3.2-5.9% of pre-T3-injection concentrations. The presence of TSH in plasma after single T3 injection and its absence (<0.25% of euthyroid values) after euthyroid rats were treated with T3, 2-4 μg/day for 43 days, indicate that, as in the hypothyroid rat, TSH suppression has both a rapid and slow component in the euthyroid rat. A small but statistically insignificant increase in TSH secretion occurred after injection of a high dose of thyrotropin-releasing hormone (TRH; 1 μg/100 g BW) into T3-treated euthyroid or hypothyroid rats. This suggested that endogenous TRH did not play an important role in maintaining TSH secretion in the presence of high plasma T3 concentrations. The metabolic clearance rate (MCR) of TSH was measured to determine whether altered rates of TSH metabolism could account for the 30-100-fold greater TSH concentration observed after 24 hr in T3-injected hypothyroid rats as compared to T3-injected euthyroid rats. Neither a mean 40% decrease in the MCR of TSH nor a 4-fold increase in number of thyrotrophs in hypothyroid rats could account for the large difference in residual TSH concentration. The TSH secretion rate per thyrotroph in non-injected or T3-injected hypothyroid rats appears to be 4-8-fold greater than in euthyroid rats.

Original languageEnglish (US)
Pages (from-to)769-775
Number of pages7
JournalEndocrinology
Volume101
Issue number3
StatePublished - 1977

Fingerprint

Thyrotropin
Injections
Thyrotrophs
Metabolic Clearance Rate
Thyrotropin-Releasing Hormone
Triiodothyronine

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Biphasic thyrotropin suppression in euthyroid and hypothyroid rats. / Surks, Martin I.; Lifschitz, B. M.

In: Endocrinology, Vol. 101, No. 3, 1977, p. 769-775.

Research output: Contribution to journalArticle

Surks, Martin I. ; Lifschitz, B. M. / Biphasic thyrotropin suppression in euthyroid and hypothyroid rats. In: Endocrinology. 1977 ; Vol. 101, No. 3. pp. 769-775.
@article{eada345dd4b24fe08e9331164557c67f,
title = "Biphasic thyrotropin suppression in euthyroid and hypothyroid rats",
abstract = "To determine whether thyrotropin (TSH) suppression was characterized by a rapid and slow component in euthyroid rats, TSH concentrations were measured in concentrates of plasma pooled from groups of 8 euthyroid rats 24 hr after injection of a single dose of triiodothyronine (T3). Plasma TSH decreased after T3 injection to values 3.2-5.9{\%} of pre-T3-injection concentrations. The presence of TSH in plasma after single T3 injection and its absence (<0.25{\%} of euthyroid values) after euthyroid rats were treated with T3, 2-4 μg/day for 43 days, indicate that, as in the hypothyroid rat, TSH suppression has both a rapid and slow component in the euthyroid rat. A small but statistically insignificant increase in TSH secretion occurred after injection of a high dose of thyrotropin-releasing hormone (TRH; 1 μg/100 g BW) into T3-treated euthyroid or hypothyroid rats. This suggested that endogenous TRH did not play an important role in maintaining TSH secretion in the presence of high plasma T3 concentrations. The metabolic clearance rate (MCR) of TSH was measured to determine whether altered rates of TSH metabolism could account for the 30-100-fold greater TSH concentration observed after 24 hr in T3-injected hypothyroid rats as compared to T3-injected euthyroid rats. Neither a mean 40{\%} decrease in the MCR of TSH nor a 4-fold increase in number of thyrotrophs in hypothyroid rats could account for the large difference in residual TSH concentration. The TSH secretion rate per thyrotroph in non-injected or T3-injected hypothyroid rats appears to be 4-8-fold greater than in euthyroid rats.",
author = "Surks, {Martin I.} and Lifschitz, {B. M.}",
year = "1977",
language = "English (US)",
volume = "101",
pages = "769--775",
journal = "Endocrinology",
issn = "0013-7227",
publisher = "The Endocrine Society",
number = "3",

}

TY - JOUR

T1 - Biphasic thyrotropin suppression in euthyroid and hypothyroid rats

AU - Surks, Martin I.

AU - Lifschitz, B. M.

PY - 1977

Y1 - 1977

N2 - To determine whether thyrotropin (TSH) suppression was characterized by a rapid and slow component in euthyroid rats, TSH concentrations were measured in concentrates of plasma pooled from groups of 8 euthyroid rats 24 hr after injection of a single dose of triiodothyronine (T3). Plasma TSH decreased after T3 injection to values 3.2-5.9% of pre-T3-injection concentrations. The presence of TSH in plasma after single T3 injection and its absence (<0.25% of euthyroid values) after euthyroid rats were treated with T3, 2-4 μg/day for 43 days, indicate that, as in the hypothyroid rat, TSH suppression has both a rapid and slow component in the euthyroid rat. A small but statistically insignificant increase in TSH secretion occurred after injection of a high dose of thyrotropin-releasing hormone (TRH; 1 μg/100 g BW) into T3-treated euthyroid or hypothyroid rats. This suggested that endogenous TRH did not play an important role in maintaining TSH secretion in the presence of high plasma T3 concentrations. The metabolic clearance rate (MCR) of TSH was measured to determine whether altered rates of TSH metabolism could account for the 30-100-fold greater TSH concentration observed after 24 hr in T3-injected hypothyroid rats as compared to T3-injected euthyroid rats. Neither a mean 40% decrease in the MCR of TSH nor a 4-fold increase in number of thyrotrophs in hypothyroid rats could account for the large difference in residual TSH concentration. The TSH secretion rate per thyrotroph in non-injected or T3-injected hypothyroid rats appears to be 4-8-fold greater than in euthyroid rats.

AB - To determine whether thyrotropin (TSH) suppression was characterized by a rapid and slow component in euthyroid rats, TSH concentrations were measured in concentrates of plasma pooled from groups of 8 euthyroid rats 24 hr after injection of a single dose of triiodothyronine (T3). Plasma TSH decreased after T3 injection to values 3.2-5.9% of pre-T3-injection concentrations. The presence of TSH in plasma after single T3 injection and its absence (<0.25% of euthyroid values) after euthyroid rats were treated with T3, 2-4 μg/day for 43 days, indicate that, as in the hypothyroid rat, TSH suppression has both a rapid and slow component in the euthyroid rat. A small but statistically insignificant increase in TSH secretion occurred after injection of a high dose of thyrotropin-releasing hormone (TRH; 1 μg/100 g BW) into T3-treated euthyroid or hypothyroid rats. This suggested that endogenous TRH did not play an important role in maintaining TSH secretion in the presence of high plasma T3 concentrations. The metabolic clearance rate (MCR) of TSH was measured to determine whether altered rates of TSH metabolism could account for the 30-100-fold greater TSH concentration observed after 24 hr in T3-injected hypothyroid rats as compared to T3-injected euthyroid rats. Neither a mean 40% decrease in the MCR of TSH nor a 4-fold increase in number of thyrotrophs in hypothyroid rats could account for the large difference in residual TSH concentration. The TSH secretion rate per thyrotroph in non-injected or T3-injected hypothyroid rats appears to be 4-8-fold greater than in euthyroid rats.

UR - http://www.scopus.com/inward/record.url?scp=0017664325&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0017664325&partnerID=8YFLogxK

M3 - Article

VL - 101

SP - 769

EP - 775

JO - Endocrinology

JF - Endocrinology

SN - 0013-7227

IS - 3

ER -