# Presentation: 668314

## Male and Female Pubertal Protocols:  Identifying Environmental Compounds That Alter The Thyroid axis

- T. Stoker
- Endocrinology Branch, RTD
- NHEERL, ORD
- U.S. EPA, RTP, NC

## Male and Female Pubertal Protocols 

**   ****Detects compounds that display:**
**anti-thyroid**
**Estrogenic**
**androgenic or anti-androgenic **
**altered puberty via changes in FSH, LH, PRL, GH or hypothalamic function.**
**anti-estrogenic [estrogen receptor (ER)]**
**steroid enzyme mediated activity****  **

**Male and Female Pubertal Protocols **

## Questions

- Are the male and female pubertal assays useful as screens for thyrotoxicants with different mechanisms of action?
- Are results reliable?
- What is Interlaboratory variability?

## Overview

- Mechanisms of altered thyroid homeostasis.
- Examples of chemicals with specific mechanisms.
- Contract study results for PB and PTU
- What was observed
- Published studies vs. current data.
- New studies looking at other thyrotoxicants (EPA, ORD)

## MECHANISMS OF ALTERED THYROID HOMEOSTASIS

- Clearance of thyroid hormones (ex. liver enzyme induction or altered TTR/TBG)
- Synthesis of thyroid hormones (ex. altered thyroperoxidase or altered uptake of iodine into the thyroid cell)
- Tissue deiodinase (peripheral conversion of T4>T3, FD & C Red No. 3, others?)
- Receptor Binding (??known)
- Brain/hypothalamic control of TRF (not known ??)

## Mechanisms of Thyroid Disruption 

**Mechanisms of Thyroid Disruption**** **

- FD&C Red No. 3

- Alachlor
- DDT

## Altered Synthesis

## Altered Thyroid Synthesis

- By altered KI symporter
- Perchlorate

- EPA, RTP
- Wistar female

## Altered Synthesis of T4

- By inhibition of thyroperoxidase
- PTU

- Marty et al.,
- Tox. Sci., 2001) Male CD

## Altered Clearance of T4

## Altered Clearance of T4

- Phenobarbital in Pubertal Male

- Marty et al.,
- Tox. Sci., 2001 Male CD

## Pubertal Assays Detecting Thyroid Toxicants

- Mechanism Identified by Assay(s)
- Altered KI symporter
- Altered thyroperoxidase activity
- Altered clearance of T4
- Mechanisms not studied to date
- Binding proteins (organochlorines, like OH-PCBs)
- Deiodinase (FD&C Red No. 3)
- Hypothalamic alterations

## Results from Contract Studies

- Contract I, 2000 (PTU)
- Thyroid Hormones
- Contract II, 2003 (PB)
- Thyroid Weights
- Contract III, 2003 (PTU &PB)
- Thyroid Hormones, Weights and Histology

## Contract Study II

- 2003

- Effect of chemicals on Thyroid Weights in
- Female Pubertal

## Contract Study II

- 2003

**The effect of chemicals on thyroid weight in**
**the Male Pubertal**

## Contract Study III

- 2003

**The effect of chemicals on thyroid weight **
**in the Female Pubertal**

## Contract Study III

- 2003

**The Effect of Chemicals on Thyroid Weight **
**in the Male Pubertal.**

## Contract Study I

- 2000

**The effect of chemicals on thyroid hormones**
**in the Male Pubertal**

## Contract Study I

- 2000

**The effect of chemicals on thyroid hormones**
**in the Female Pubertal**

## Contract Study III

- 2003

**The effect of chemicals on thyroid hormones **
**in the Female Pubertal.**

## Contract Study III

- 2003

## Summary of Contract Studies

- All studies found alterations in thyroid parameters that were consistent with the chemical action
- Thyroid Weights
- Both Contract II and III found appropriate differences in weights, Contract I did not take weights.
- Thyroid Hormones
- PTU
- Contract I and III identified PTU thyroid hormone effects (T4 and TSH)
- Contract II did not test PTU
- PB
- Contract III identified changes in TSH, but no T4 decrease
- Contract II did not measure hormones

## Identifying other chemicals (ORD studies)

- Perchlorate- KI symporter
- DE-71- Liver metabolism of T4

## The Effect of Perchlorate on Thyroid

**Endpoints in the Male Pubertal**

- EPA Special Study
- Wistar Rat

## EPA Special Study

**Female Pubertal Protocol**

- Wistar Rat

## EPA Special Study

**The Effect of DE-71 on Thyroid Endpoints in the **
**Male Pubertal Protocol**

- Wistar Rat

## EPA Special Study

**The Effect of DE-71 on thyroid endpoints in the **
**Female Pubertal Protocol**

- Wistar Rat

## T3 in DE-71 StudyComparison of Male and Female

- EPA Study
- Wistar Rat

## Thyroid Histopathology (hypo)

- Decreased Colloid Area
- Increased Follicular proliferation and cell heights.

## Hypothyroidism

- EPA DE-71 Study

- Control Male Thyroid

- 60 mg/kg DE-71 Male Thyroid

- Also observed in female 60 mg/kg DE-71.

## Conclusions

- Male and Female Pubertals.
- No failures so far
- 3 mechanisms examined
- Do we need to do other mechanisms, before moving on? 5’ Deiodinase inhibitor, TTR, hypothalamus??
- Some disappointments (maybe)
- One contract lab missed PB effect on T4
- Still thyroid effects observed! (TSH, liver, thyroid wt.)

## Slide 32

## Marty et al., 

- Marty et al.,
- Tox. Sci., 2001)

## O’Connor, 1999

- 15 Day SD Male

**The Effect of PB and PTU on Liver**
**in the Intact 15 Day Male Assay **

## O’Connor, 1999

**The Effect of PB on Thyroid Hormones**
**in the 15 Day Intact Male SD**

## O’Connor

## Studies

- Contract studies
- Therimmune 2000
- PTU (240) , male and female in SD and LE
- Therimmune 2003
- PB (25, 50, 100 mg/kg) male and female SD
- RTI
- PTU (2 and 25 mg/kg) male and female SD
- PB (50 and 100 mg/kg) male and female SD
- EPA studies
- PBDE and perchlorate.
- Industry studies
- Marty et al., PB 50 and 100 mg/kg and PTU 240 mg/kg in male SD
- O’Connor et al., PB 5, 25, and 50 mg/kg or PTU .025, .25, 1 and 10 mg/kg in SD males (15 day intact)
- Yamada, PB at 125 mg/kg and PTU at 2.5 mg/kg (10 day HERSH)

- Contract Study III
- 2003

**The effect of chemicals on liver weight**
**in the Male and Female Pubertal**

## Effect of chemicals on liver weight in Male and Female Pubertals

- Contract Study II
- 2003

- Female

- Male

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